U.S. patent application number 12/785897 was filed with the patent office on 2011-11-24 for thermally-assisted magnetic recording head including plasmon generator.
This patent application is currently assigned to TDK CORPORATION. Invention is credited to Susumu AOKI, Tsutomu CHOU, Takahiko IZAWA, Daisuke MIYAUCHI, Tetsuya ROPPONGI, Kosuke TANAKA, Takeshi TSUTSUMI.
Application Number | 20110286128 12/785897 |
Document ID | / |
Family ID | 44972344 |
Filed Date | 2011-11-24 |
United States Patent
Application |
20110286128 |
Kind Code |
A1 |
TSUTSUMI; Takeshi ; et
al. |
November 24, 2011 |
THERMALLY-ASSISTED MAGNETIC RECORDING HEAD INCLUDING PLASMON
GENERATOR
Abstract
A plasmon generator has an outer surface including a plasmon
exciting part that faces an evanescent light generating surface of
a waveguide. The outer surface further includes first and second
inclined surfaces that increase in distance from each other with
increasing distance from the plasmon exciting part, and a front end
face. The front end face has first and second portions that are
connected to each other into a V-shape. The first portion includes
a first side lying at an end of the first inclined surface. The
second portion includes a second side lying at an end of the second
inclined surface. An angle formed between a lower part of the first
side and a lower part of the second side is smaller than that
formed between an upper part of the first side and an upper part of
the second side.
Inventors: |
TSUTSUMI; Takeshi; (Tokyo,
JP) ; MIYAUCHI; Daisuke; (Toyko, JP) ;
ROPPONGI; Tetsuya; (Tokyo, JP) ; TANAKA; Kosuke;
(Tokyo, JP) ; AOKI; Susumu; (Tokyo, JP) ;
IZAWA; Takahiko; (Tokyo, JP) ; CHOU; Tsutomu;
(Tokyo, JP) |
Assignee: |
TDK CORPORATION
Tokyo
JP
|
Family ID: |
44972344 |
Appl. No.: |
12/785897 |
Filed: |
May 24, 2010 |
Current U.S.
Class: |
360/59 ;
29/603.07; G9B/5.026 |
Current CPC
Class: |
G11B 5/6088 20130101;
G11B 5/3116 20130101; G11B 5/1278 20130101; G11B 5/3163 20130101;
B82Y 20/00 20130101; G11B 7/1384 20130101; G11B 7/1387 20130101;
Y10T 29/49032 20150115; G02B 5/008 20130101; G02B 6/1226 20130101;
G11B 2005/0021 20130101; G11B 5/314 20130101 |
Class at
Publication: |
360/59 ;
29/603.07; G9B/5.026 |
International
Class: |
G11B 5/02 20060101
G11B005/02; G11B 5/127 20060101 G11B005/127 |
Claims
1. A thermally-assisted magnetic recording head comprising: a
medium facing surface that faces a magnetic recording medium; a
magnetic pole that has an end face located in the medium facing
surface and produces a write magnetic field for writing data on the
magnetic recording medium; a waveguide including a core and a clad,
the core propagating light; and a plasmon generator, wherein: the
core has an evanescent light generating surface that generates
evanescent light based on the light propagated through the core;
the plasmon generator has an outer surface including a plasmon
exciting part, and has a near-field light generating part lying at
an end of the plasmon exciting part and located in the medium
facing surface, the plasmon exciting part facing the evanescent
light generating surface with a predetermined distance
therebetween, the plasmon generator being located above the
evanescent light generating surface; a surface plasmon is excited
on the plasmon exciting part through coupling with the evanescent
light generated from the evanescent light generating surface; the
near-field light generating part generates near-field light based
on the surface plasmon excited on the plasmon exciting part; the
outer surface of the plasmon generator further includes first and
second inclined surfaces that are each connected to the plasmon
exciting part, and a front end face that is located in the medium
facing surface and connected to the first and second inclined
surfaces, the first and second inclined surfaces increasing in
distance from each other with increasing distance from the plasmon
exciting part; the front end face has first and second portions
that are connected to each other into a V-shape, and the end face
of the magnetic pole has a portion interposed between the first and
second portions of the front end face; the first portion includes a
first side that lies at an end of the first inclined surface; the
second portion includes a second side that lies at an end of the
second inclined surface; each of the first side and the second side
includes an upper part and a lower part that are continuous with
each other; and an angle formed between the lower part of the first
side and the lower part of the second side is smaller than that
formed between the upper part of the first side and the upper part
of the second side.
2. The thermally-assisted magnetic recording head according to
claim 1, wherein: the front end face has a bottom end that is
closer to the evanescent light generating surface; and a distance
between the bottom end and a virtual straight line that passes
through a border between the upper and lower parts of the first
side and a border between the upper and lower parts of the second
side falls within a range of 10 to 25 nm.
3. The thermally-assisted magnetic recording head according to
claim 1, wherein: the plasmon exciting part includes a propagative
edge that connects respective ends of the first and second inclined
surfaces to each other, the respective ends being closer to the
evanescent light generating surface; and the near-field light
generating part lies at an end of the propagative edge.
4. The thermally-assisted magnetic recording head according to
claim 3, wherein: the plasmon generator has a V-shaped portion that
includes the propagative edge and the front end face, the V-shaped
portion being V-shaped in cross section parallel to the medium
facing surface; and the magnetic pole includes a portion
accommodated in the V-shaped portion.
5. The thermally-assisted magnetic recording head according to
claim 1, wherein: the plasmon exciting part includes a flat surface
part that connects respective ends of the first and second inclined
surfaces to each other, the respective ends being closer to the
evanescent light generating surface; and the flat surface part
includes a width changing portion, the width changing portion
having a width that decreases with decreasing distance to the
medium facing surface, the width being in a direction parallel to
the medium facing surface and the evanescent light generating
surface.
6. The thermally-assisted magnetic recording head according to
claim 5, wherein: the width changing portion has a front end part
that is closer to the medium facing surface, the front end part
being located at a distance from the medium facing surface; and the
plasmon exciting part further has a propagative edge that connects
the front end part of the width changing portion to the near-field
light generating part.
7. The thermally-assisted magnetic recording head according to
claim 5, wherein: the plasmon generator has a bottom part that is
shaped like a plate and two sidewall parts that are each shaped
like a plate, the bottom part including the width changing portion,
the two sidewall parts being located farther from the evanescent
light generating surface than is the bottom part and connected to
opposite ends of the bottom part in the direction parallel to the
medium facing surface and the evanescent light generating surface;
the bottom part has a width that decreases with decreasing distance
to the medium facing surface, the width being in the direction
parallel to the medium facing surface and the evanescent light
generating surface; a distance between the two sidewall parts in
the direction parallel to the medium facing surface and the
evanescent light generating surface increases with increasing
distance from the evanescent light generating surface, and
decreases with decreasing distance to the medium facing surface;
the first and second inclined surfaces include respective surfaces
of the two sidewall parts, the respective surfaces lying on
opposite sides in the direction parallel to the medium facing
surface and the evanescent light generating surface; and the
magnetic pole includes a portion that is accommodated in a space
formed by the bottom part and the two sidewall parts so as to be in
contact with the bottom part and the two sidewall parts.
8. The thermally-assisted magnetic recording head according to
claim 1, further comprising a buffer part that is located between
the evanescent light generating surface and the plasmon exciting
part and has a refractive index lower than that of the core.
9. A head gimbal assembly comprising: the thermally-assisted
magnetic recording head according to claim 1; and a suspension that
supports the thermally-assisted magnetic recording head.
10. A magnetic recording device comprising: a magnetic recording
medium; the thermally-assisted magnetic recording head according to
claim 1; and a positioning device that supports the
thermally-assisted magnetic recording head and positions the
thermally-assisted magnetic recording head with respect to the
magnetic recording medium.
11. A method of manufacturing the thermally-assisted magnetic
recording head according to claim 1, comprising the steps of:
forming the waveguide; forming the plasmon generator after the
formation of the waveguide; and forming the magnetic pole after the
formation of the plasmon generator, wherein: the step of forming
the waveguide includes the steps of forming the core; and forming a
clad layer that constitutes at least part of the clad; the clad
layer has a top surface that is located above the core, and a
groove that opens in the top surface of the clad layer and is
located above the core; and the groove has first and second
sidewalls that decrease in distance from each other with increasing
distance from the top surface of the clad layer, the method further
comprising the step of forming a dielectric film in the groove,
between the step of forming the waveguide and the step of forming
the plasmon generator, the dielectric film being intended for
determining a shape of the plasmon generator, wherein the groove
and the dielectric film constitute an accommodating part for
accommodating the plasmon generator, and the plasmon generator is
formed to be accommodated in the accommodating part.
12. The method according to claim 11, wherein: the dielectric film
includes a first film portion that adheres to the first sidewall,
and a second film portion that adheres to the second sidewall; each
of the first film portion and the second film portion includes an
upper part and a lower part that are continuous with each other; in
the first film portion, the lower part has a thickness smaller than
that of the upper part in a direction perpendicular to the first
sidewall; and in the second film portion, the lower part has a
thickness smaller than that of the upper part in a direction
perpendicular to the second sidewall.
13. The method according to claim 12, wherein the dielectric film
is formed by sputtering.
14. Method according to claim 12, wherein: the dielectric film is
formed by ion beam sputtering; when forming the first film portion,
a traveling direction of a center of a material particle flow for
forming the first film portion forms a greater angle with respect
to a direction perpendicular to the top surface of the clad layer
than an angle that the second sidewall forms with respect to the
direction perpendicular to the top surface of the clad layer; and
when forming the second film portion, a traveling direction of a
center of a material particle flow for forming the second film
portion forms a greater angle with respect to the direction
perpendicular to the top surface of the clad layer than an angle
that the first sidewall forms with respect to the direction
perpendicular to the top surface of the clad layer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a thermally-assisted
magnetic recording head including a plasmon generator for use in
thermally-assisted magnetic recording where a magnetic recording
medium is irradiated with near-field light to lower the coercivity
of the magnetic recording medium for data writing.
[0003] 2. Description of the Related Art
[0004] Recently, magnetic recording devices such as magnetic disk
drives have been improved in recording density, and thin-film
magnetic heads and magnetic recording media of improved performance
have been demanded accordingly. Among the thin-film magnetic heads,
a composite thin-film magnetic head has been used widely. The
composite thin-film magnetic head has such a structure that a read
head including a magnetoresistive element (hereinafter, also
referred to as MR element) intended for reading and a write head
including an induction-type electromagnetic transducer intended for
writing are stacked on a substrate. In a magnetic disk drive, the
thin-film magnetic head is mounted on a slider that flies slightly
above the surface of the magnetic recording medium.
[0005] Magnetic recording media are discrete media each made of an
aggregate of magnetic fine particles, each magnetic fine particle
forming a single-domain structure. A single recording bit of a
magnetic recording medium is composed of a plurality of magnetic
fine particles. For improved recording density, it is necessary to
reduce asperities at the borders between adjoining recording bits.
To achieve this, the magnetic fine particles must be made smaller.
However, making the magnetic fine particles smaller causes the
problem that the thermal stability of magnetization of the magnetic
fine particles decreases with decreasing volume of the magnetic
fine particles. To solve this problem, it is effective to increase
the anisotropic energy of the magnetic fine particles. However,
increasing the anisotropic energy of the magnetic fine particles
leads to an increase in coercivity of the magnetic recording
medium, and this makes it difficult to perform data writing with
existing magnetic heads.
[0006] To solve the foregoing problems, there has been proposed a
technique so-called thermally-assisted magnetic recording. This
technique uses a magnetic recording medium having high coercivity.
When writing data, a magnetic field and heat are simultaneously
applied to the area of the magnetic recording medium where to write
data, so that the area rises in temperature and drops in coercivity
for data writing. Hereinafter, a magnetic head for use in
thermally-assisted magnetic recording will be referred to as a
thermally-assisted magnetic recording head.
[0007] In thermally-assisted magnetic recording, near-field light
is typically used as a means for applying heat to the magnetic
recording medium. A commonly known method for generating near-field
light is to use a near-field optical probe or so-called plasmon
antenna, which is a piece of metal that generates near-field light
from plasmons excited by irradiation with light.
[0008] However, the plasmon antenna which generates near-field
light by direct irradiation with light is known to exhibit very low
efficiency of transformation of the applied light into near-field
light. The energy of the light applied to the plasmon antenna is
mostly reflected off the surface of the plasmon antenna, or
transformed into thermal energy and absorbed by the plasmon
antenna. The plasmon antenna is small in volume since the size of
the plasmon antenna is set to be smaller than or equal to the
wavelength of the light. The plasmon antenna therefore shows a
significant increase in temperature when it absorbs the thermal
energy.
[0009] Such a temperature increase makes the plasmon antenna expand
in volume and protrude from a medium facing surface, which is the
surface of the thermally-assisted magnetic recording head to face
the magnetic recording medium. This causes an end of the read head
located in the medium facing surface to get farther from the
magnetic recording medium, thereby causing the problem that a servo
signal cannot be read during write operations.
[0010] There has been known a technique in which a dielectric and a
metal are arranged to face each other with a predetermined gap
therebetween, and surface plasmons are excited on the metal by
utilizing evanescent light that results from the total reflection
of the light propagated through the dielectric at the surface of
the dielectric. As a related technique, U.S. Pat. No. 7,454,095
discloses a technique in which a metal waveguide and a dielectric
waveguide are arranged to face each other with a predetermined gap
therebetween, and the metal waveguide is coupled with the
dielectric waveguide in a surface plasmon mode. It is then
conceivable to establish coupling between the light propagated
through the waveguide's core and a plasmon generator, a piece of
metal, in a surface plasmon mode through a buffer part so that
surface plasmons are excited on the plasmon generator, instead of
directly irradiating the plasmon generator with the light.
According to such a technique, it is possible to transform the
light propagated through the core into near-field light with high
efficiency. Since the plasmon generator is not directly irradiated
with the light propagated through the core, it is also possible to
prevent the plasmon generator from excessively increasing in
temperature.
[0011] The plasmon generator may be shaped to have an edge part
that faces the outer surface of the core with a predetermined
distance therebetween. An example of such a shape is a
triangular-prism shape. Such a plasmon generator has a front end
face that is located in the medium facing surface. The front end
face includes a tip that lies at an end of the edge part to form a
near-field light generating part. The plasmon generator includes
two inclined surfaces that are each connected to the edge part, the
two inclined surfaces increasing in distance from each other with
increasing distance from the edge part. In the plasmon generator,
surface plasmons are excited on the edge part through coupling with
the evanescent light that occurs from the outer surface of the
core. The surface plasmons are propagated along the edge part to
the near-field light generating part located in the medium facing
surface, and the near-field light generating part generates
near-field light based on the surface plasmons. With such a plasmon
generator, it is possible to propagate the surface plasmons excited
on the edge part to the near-field light generating part with high
efficiency.
[0012] In the foregoing plasmon generator, the edge part is ideally
formed into a linear shape by the contact of the two inclined
surfaces with each other with a predetermined angle formed
therebetween. In an actually fabricated plasmon generator, however,
the edge part is rounded and thereby has a cylindrical surface
configuration that connects the two inclined surfaces forming a
predetermined angle therebetween. As employed herein, the radius of
curvature of the edge part having the cylindrical surface
configuration will be referred to as point radius. The angle that
each of the two inclined surfaces forms with respect to the
direction perpendicular to the surface of the core that the edge
part faces will be referred to as inclination angle. As will be
described below, the point radius and the inclination angle of the
plasmon generator used in a thermally-assisted magnetic recording
head are significant parameters that affect the characteristics of
the thermally-assisted magnetic recording head.
[0013] First, the point radius will be described. The point radius
is a parameter that affects the spot diameter of the near-field
light occurring from the near-field light generating part. In order
to increase the recording density of a magnetic recording device, a
smaller spot diameter is preferred for the near-field light. To
reduce the spot diameter of the near-field light, a smaller point
radius is preferred.
[0014] Next, the inclination angle will be described. To increase
the use efficiency of the light propagated through the core of the
waveguide, it is important to increase the intensity of the surface
plasmons excited on the plasmon generator. This requires that the
wave number of the evanescent light and the wave number of the
surface plasmons excited on the plasmon generator be matched with
each other. The wave number of the surface plasmons excited on the
plasmon generator varies according to the shape of the plasmon
generator. The inclination angle is thus a parameter that affects
the wave number of the surface plasmons excited on the plasmon
generator. Meanwhile, the wave number of the evanescent light
depends on the wavelength of the light propagated through the core.
When typical laser light is used as the light to be propagated
through the core, it is necessary that the wave number of the
surface plasmons to be excited on the plasmon generator be matched
with the wave number of the evanescent light which depends on the
wavelength of the laser light. This means that there is a preferred
range for the inclination angle.
[0015] As seen above, for a plasmon generator having an edge part
that faces the core with a buffer part therebetween, the
inclination angle needs to fall within the preferred range in order
to increase the use efficiency of the light propagated through the
core, and the point radius needs to be made smaller in order to
make the spot diameter of the near-field light smaller. In order to
make the point radius smaller, it is effective to make the
inclination angle smaller so that the front end face of the plasmon
generator has a tip of more sharply pointed shape. Making the
inclination angle smaller, however, gives rise to the problem that
the wave number of the surface plasmons to be excited on the
plasmon generator does not match with the wave number of the
evanescent light. This decreases the surface plasmons to be excited
on the edge part, thereby decreasing the use efficiency of the
light propagated through the core.
[0016] When a thermally-assisted magnetic recording head employs
such a configuration that the light propagated through the core is
coupled with the plasmon generator in a surface plasmon mode
through a buffer part, there arises the following problem if the
position of occurrence of the write magnetic field and the position
of occurrence of the near-field light are located close to each
other. That is, in such a case, both the core and the magnetic pole
need to be located near the plasmon generator. It follows that the
magnetic pole is located near the core. The magnetic pole is
typically made of a magnetic metal material. The presence of such a
magnetic pole near the core causes the problem that part of the
light propagated through the core is absorbed by the magnetic pole
and the use efficiency of the light propagated through the core
thereby decreases.
OBJECT AND SUMMARY OF THE INVENTION
[0017] It is an object of the present invention to provide a
thermally-assisted magnetic recording head that allows efficient
use of the light propagated through the core of the waveguide,
allows generation of near-field light having a small spot diameter
from the plasmon generator, and allows the position of occurrence
of the write magnetic field and the position of the occurrence of
the near-field light to be close to each other, and to provide a
method of manufacturing the thermally-assisted magnetic recording
head, and a head gimbal assembly and a magnetic recording device
that each include the thermally-assisted magnetic recording
head.
[0018] A thermally-assisted magnetic recording head of the present
invention includes: a medium facing surface that faces a magnetic
recording medium; a magnetic pole that has an end face located in
the medium facing surface and produces a write magnetic field for
writing data on the magnetic recording medium; a waveguide
including a core and a clad, the core propagating light; and a
plasmon generator.
[0019] The core has an evanescent light generating surface that
generates evanescent light based on the light propagated through
the core. The plasmon generator has an outer surface including a
plasmon exciting part, and has a near-field light generating part
lying at an end of the plasmon exciting part and located in the
medium facing surface. The plasmon exciting part faces the
evanescent light generating surface with a predetermined distance
therebetween. The plasmon generator is located above the evanescent
light generating surface. A surface plasmon is excited on the
plasmon exciting part through coupling with the evanescent light
generated from the evanescent light generating surface. The
near-field light generating part generates near-field light based
on the surface plasmon excited on the plasmon exciting part.
[0020] The outer surface of the plasmon generator further includes
first and second inclined surfaces that are each connected to the
plasmon exciting part, and a front end face that is located in the
medium facing surface and connected to the first and second
inclined surfaces. The first and second inclined surfaces increase
in distance from each other with increasing distance from the
plasmon exciting part. The front end face has first and second
portions that are connected to each other into a V-shape. The end
face of the magnetic pole has a portion interposed between the
first and second portions of the front end face. The first portion
includes a first side that lies at an end of the first inclined
surface. The second portion includes a second side that lies at an
end of the second inclined surface. Each of the first side and the
second side includes an upper part and a lower part that are
continuous with each other. An angle formed between the lower part
of the first side and the lower part of the second side is smaller
than that formed between the upper part of the first side and the
upper part of the second side.
[0021] In the thermally-assisted magnetic recording head of the
present invention, the front end face may have a bottom end that is
closer to the evanescent light generating surface. The distance
between the bottom end and a virtual straight line that passes
through the border between the upper and lower parts of the first
side and the border between the upper and lower parts of the second
side may fall within the range of 10 to 25 nm.
[0022] In the thermally-assisted magnetic recording head of the
present invention, the plasmon exciting part may include a
propagative edge that connects respective ends of the first and
second inclined surfaces to each other, the respective ends being
closer to the evanescent light generating surface. The near-field
light generating part may lie at an end of the propagative edge. In
such a case, the plasmon generator may have a V-shaped portion that
includes the propagative edge and the front end face. The V-shaped
portion is V-shaped in cross section parallel to the medium facing
surface. The magnetic pole may include a portion accommodated in
the V-shaped portion.
[0023] In the thermally-assisted magnetic recording head of the
present invention, the plasmon exciting part may include a flat
surface part that connects respective ends of the first and second
inclined surfaces to each other, the respective ends being closer
to the evanescent light generating surface. In such a case, the
flat surface part may include a width changing portion. The width
changing portion has a width that decreases with decreasing
distance to the medium facing surface, the width being in a
direction parallel to the medium facing surface and the evanescent
light generating surface. The width changing portion may have a
front end part that is closer to the medium facing surface. The
front end part may be located at a distance from the medium facing
surface. The plasmon exciting part may further have a propagative
edge that connects the front end part of the width changing portion
to the near-field light generating part.
[0024] In the thermally-assisted magnetic recording head of the
present invention, when the plasmon exciting part includes the flat
surface part and the flat surface part includes the width changing
portion, the plasmon generator may have a bottom part that is
shaped like a plate and two sidewall parts that are each shaped
like a plate. The bottom part includes the width changing portion.
The two sidewall parts are located farther from the evanescent
light generating surface than is the bottom part and are connected
to opposite ends of the bottom part in the direction parallel to
the medium facing surface and the evanescent light generating
surface. The bottom part has a width that decreases with decreasing
distance to the medium facing surface, the width being in the
direction parallel to the medium facing surface and the evanescent
light generating surface. The distance between the two sidewall
parts in the direction parallel to the medium facing surface and
the evanescent light generating surface increases with increasing
distance from the evanescent light generating surface, and
decreases with decreasing distance to the medium facing surface.
The first and second inclined surfaces include respective surfaces
of the two sidewall parts, the respective surfaces lying on
opposite sides in the direction parallel to the medium facing
surface and the evanescent light generating surface. The magnetic
pole may include a portion that is accommodated in a space formed
by the bottom part and the two sidewall parts so as to be in
contact with the bottom part and the two sidewall parts.
[0025] The thermally-assisted magnetic recording head of the
present invention may further include a buffer part that is located
between the evanescent light generating surface and the plasmon
exciting part and has a refractive index lower than that of the
core.
[0026] A head gimbal assembly of the present invention includes:
the thermally-assisted magnetic recording head of the present
invention; and a suspension that supports the thermally-assisted
magnetic recording head. A magnetic recording device of the present
invention includes: a magnetic recording medium; the
thermally-assisted magnetic recording head of the present
invention; and a positioning device that supports the
thermally-assisted magnetic recording head and positions the same
with respect to the magnetic recording medium.
[0027] A method of manufacturing the thermally-assisted magnetic
recording head of the present invention includes the steps of
forming the waveguide; forming the plasmon generator after the
formation of the waveguide; and forming the magnetic pole after the
formation of the plasmon generator.
[0028] The step of forming the waveguide includes the steps of:
forming the core; and forming a clad layer that constitutes at
least part of the clad. The clad layer has a top surface that is
located above the core, and a groove that opens in the top surface
of the clad layer and is located above the core. The groove has
first and second sidewalls that decrease in distance from each
other with increasing distance from the top surface of the clad
layer.
[0029] The method of manufacturing the thermally-assisted magnetic
recording head of the present invention further includes the step
of forming a dielectric film in the groove, between the step of
forming the waveguide and the step of forming the plasmon
generator, the dielectric film being intended for determining a
shape of the plasmon generator. The groove and the dielectric film
constitute an accommodating part for accommodating the plasmon
generator. The plasmon generator is formed to be accommodated in
the accommodating part.
[0030] In the method of manufacturing the thermally-assisted
magnetic recording head of the present invention, the dielectric
film may include a first film portion that adheres to the first
sidewall, and a second film portion that adheres to the second
sidewall. Each of the first film portion and the second film
portion may include an upper part and a lower part that are
continuous with each other. In the first film portion, the lower
part has a thickness smaller than that of the upper part in a
direction perpendicular to the first sidewall. In the second film
portion, the lower part has a thickness smaller than that of the
upper part in a direction perpendicular to the second sidewall. In
such a case, the dielectric film may be formed by sputtering.
Alternatively, the dielectric film may be formed by ion beam
sputtering. If the dielectric film is formed by ion beam
sputtering, the traveling direction of a center of a material
particle flow for forming the first film portion may form a greater
angle with respect to a direction perpendicular to the top surface
of the clad layer than an angle that the second sidewall forms with
respect to the direction perpendicular to the top surface of the
clad layer, when forming the first film portion. When forming the
second film portion, the traveling direction of a center of a
material particle flow for forming the second film portion may form
a greater angle with respect to the direction perpendicular to the
top surface of the clad layer than an angle that the first sidewall
forms with respect to the direction perpendicular to the top
surface of the clad layer.
[0031] According to the present invention, a surface plasmon is
excited on the plasmon exciting part of the plasmon generator
through coupling with the evanescent light generated from the
evanescent light generating surface of the core of the waveguide.
The near-field light generating part generates near-field light
based on the surface plasmon. According to the present invention,
it is thereby possible to transform the light propagated through
the core into near-field light with high efficiency.
[0032] In the present invention, the outer surface of the plasmon
generator includes the first and second inclined surfaces and the
front end face. The front end face has the first and second
portions connected to each other into a V-shape. The first portion
includes the first side lying at the end of the first inclined
surface. The second portion includes the second side lying at the
end of the second inclined surface. Each of the first side and the
second side includes the upper and lower parts continuous with each
other. The angle formed between the lower part of the first side
and the lower part of the second side is smaller than that formed
between the upper part of the first side and the upper part of the
second side. Consequently, according to the present invention, it
is possible to match the wave number of the surface plasmons to be
excited on the plasmon generator with the wave number of the
evanescent light, and to reduce the spot diameter of the near-field
light by making the angle between the lower part of the first side
and the lower part of the second side smaller. The present
invention thus makes it possible to use the light propagated
through the core of the waveguide with high efficiency and to
produce near-field light with a small spot diameter from the
plasmon generator.
[0033] In the present invention, the end face of the magnetic pole
located in the medium facing surface has the portion interposed
between the first and second portions of the front end face.
Consequently, according to the present invention, it is possible to
locate the position of occurrence of the write magnetic field and
the position of occurrence of the near-field light close to each
other.
[0034] Other and further objects, features and advantages of the
present invention will appear more fully from the following
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a perspective view showing a waveguide's core, a
plasmon generator, and a magnetic pole of a thermally-assisted
magnetic recording head according to a first embodiment of the
invention.
[0036] FIG. 2 is an exploded perspective view of the plasmon
generator and the magnetic pole shown in FIG. 1.
[0037] FIG. 3 is a perspective view showing the core and the
plasmon generator shown in FIG. 1.
[0038] FIG. 4 is a front view showing a part of the medium facing
surface of a head unit of the thermally-assisted magnetic recording
head according to the first embodiment of the invention.
[0039] FIG. 5 is an enlarged front view of a part of the core and
the plasmon generator shown in FIG. 4.
[0040] FIG. 6 is a cross-sectional view showing the core, the
plasmon generator, and the magnetic pole of the thermally-assisted
magnetic recording head according to the first embodiment of the
invention.
[0041] FIG. 7 is a plan view of the plasmon generator shown in FIG.
1.
[0042] FIG. 8 is a perspective view showing a magnetic recording
device according to the first embodiment of the invention.
[0043] FIG. 9 is a perspective view showing a head gimbal assembly
according to the first embodiment of the invention.
[0044] FIG. 10 is a perspective view showing the thermally-assisted
magnetic recording head according to the first embodiment of the
invention.
[0045] FIG. 11 shows a cross section taken along line 11-11 of FIG.
10.
[0046] FIG. 12 is a plan view showing a part of the head unit of
the thermally-assisted magnetic recording head according to the
first embodiment of the invention.
[0047] FIG. 13 is a block diagram showing the circuit configuration
of the magnetic recording device according to the first embodiment
of the invention.
[0048] FIG. 14 is a cross-sectional view showing a step of a method
of manufacturing the thermally-assisted magnetic recording head
according to the first embodiment of the invention.
[0049] FIG. 15 is a cross-sectional view showing a step that
follows the step of FIG. 14.
[0050] FIG. 16 is a cross-sectional view showing a step that
follows the step of FIG. 15.
[0051] FIG. 17 is a cross-sectional view showing a step that
follows the step of FIG. 16.
[0052] FIG. 18 is a cross-sectional view showing a step that
follows the step of FIG. 17.
[0053] FIG. 19 is a cross-sectional view showing a step that
follows the step of FIG. 18.
[0054] FIG. 20 is a cross-sectional view showing a step that
follows the step of FIG. 19.
[0055] FIG. 21 is a cross-sectional view showing a step that
follows the step of FIG. 20.
[0056] FIG. 22 is a characteristic chart showing the light spot
diameters and the maximum light densities of a plurality of models
of first type.
[0057] FIG. 23 is a characteristic chart showing the light spot
diameters and the maximum light densities of a plurality of models
of second type.
[0058] FIG. 24 is a characteristic chart showing the light spot
diameters and the maximum light densities of a plurality of models
of third type.
[0059] FIG. 25 is a front view showing a part of the medium facing
surface of a head unit of a thermally-assisted magnetic recording
head according to a second embodiment of the invention.
[0060] FIG. 26 is a perspective view showing a waveguide's core, a
plasmon generator, and a magnetic pole of a thermally-assisted
magnetic recording head according to a third embodiment of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0061] Preferred embodiments of the present invention will now be
described in detail with reference to the drawings. First,
reference is made to FIG. 8 to describe a magnetic disk drive that
functions as a magnetic recording device according to a first
embodiment of the invention. As shown in FIG. 8, the magnetic disk
drive includes a plurality of magnetic disks 201 as a plurality of
magnetic recording media, and a spindle motor 202 for rotating the
plurality of magnetic disks 201. The magnetic disks 201 of the
present embodiment are for use in perpendicular magnetic recording.
Each magnetic disk 201 has such a structure that a soft magnetic
backing layer, a middle layer, and a magnetic recording layer
(perpendicular magnetization layer) are stacked in this order on a
disk substrate.
[0062] The magnetic disk drive further includes an assembly
carriage device 210 having a plurality of driving arms 211, and a
plurality of head gimbal assemblies 212 attached to respective
distal ends of the driving arms 211. Each head gimbal assembly 212
includes a thermally-assisted magnetic recording head 1 according
to the present embodiment, and a suspension 220 that supports the
thermally-assisted magnetic recording head 1.
[0063] The assembly carriage device 210 is a device for positioning
each thermally-assisted magnetic recording head 1 on tracks that
are formed in the magnetic recording layer of each magnetic disk
201 and that have recording bits aligned thereon. The assembly
carriage device 210 further has a pivot bearing shaft 213 and a
voice coil motor 214. The plurality of driving arms 211 are stacked
in a direction along the pivot bearing shaft 213 and are pivotable
about the shaft 213 by being driven by the voice coil motor 214.
The magnetic recording device of the present invention is not
structurally limited to the magnetic disk drive having the
above-described configuration. For example, the magnetic recording
device of the present invention may be provided with a single
magnetic disk 201, a single driving arm 211, a single head gimbal
assembly 212 and a single thermally-assisted magnetic recording
head 1.
[0064] The magnetic disk drive further includes a control circuit
230 that controls the read/write operations of the
thermally-assisted magnetic recording heads 1 and also controls the
light emitting operation of a laser diode serving as a light source
for generating laser light for thermally-assisted magnetic
recording described later.
[0065] FIG. 9 is a perspective view showing the head gimbal
assembly 212 of FIG. 8. As previously described, the head gimbal
assembly 212 includes the thermally-assisted magnetic recording
head 1 and the suspension 220. The suspension 220 has a load beam
221, a flexure 222 fixed to the load beam 221 and having
flexibility, a base plate 223 provided at the base part of the load
beam 221, and a wiring member 224 provided on the load beam 221 and
the flexure 222. The wiring member 224 includes a plurality of
leads. The thermally-assisted magnetic recording head 1 is fixed to
the flexure 222 at the distal end of the suspension 220 such that
the head 1 faces the surface of the magnetic disk 201 with a
predetermined spacing (flying height). One end of the wiring member
224 is electrically connected to a plurality of terminals of the
thermally-assisted magnetic recording head 1. The other end of the
wiring member 224 is provided with a plurality of pad-shaped
terminals arranged at the base part of the load beam 221.
[0066] The assembly carriage device 210 and the suspension 220
correspond to the positioning device of the present invention. The
head gimbal assembly of the present invention is not limited to the
one having the configuration shown in FIG. 9. For example, the head
gimbal assembly of the present invention may have an IC chip for
driving the head that is mounted somewhere along the suspension
220.
[0067] The configuration of the thermally-assisted magnetic
recording head 1 according to the present embodiment will now be
described with reference to FIG. 10 to FIG. 12. FIG. 10 is a
perspective view showing the thermally-assisted magnetic recording
head 1. FIG. 11 shows a cross section taken along line 11-11 of
FIG. 10. FIG. 12 is a plan view showing a part of a head unit of
the thermally-assisted magnetic recording head. The
thermally-assisted magnetic recording head 1 includes a slider 10
and a light source unit 50. FIG. 11 shows the state where the
slider 10 and the light source unit 50 are separated from each
other.
[0068] The slider 10 includes a slider substrate 11 and a head unit
12. The slider substrate 11 is rectangular-solid-shaped and is made
of a ceramic material such as aluminum oxide-titanium carbide
(Al.sub.2O.sub.3--TiC). The slider substrate 11 has a medium facing
surface 11a that faces the magnetic disk 201, a rear surface lib on
the opposite side from the medium facing surface 11a, and four
surfaces that connect the medium facing surface 11a to the rear
surface lib. One of the four surfaces that connect the medium
facing surface 11a to the rear surface 11b is an element-forming
surface 11c. The element-forming surface 11c is perpendicular to
the medium facing surface 11a. The head unit 12 is disposed on the
element-forming surface 11c. The medium facing surface 11a is
processed so as to obtain an appropriate flying height of the
slider 10 with respect to the magnetic disk 201. The head unit 12
has a medium facing surface 12a that faces the magnetic disk 201,
and a rear surface 12b on the opposite side from the medium facing
surface 12a. The medium facing surface 12a is parallel to the
medium facing surface 11a of the slider substrate 11.
[0069] Where the components of the head unit 12 are concerned, with
respect to a reference position, a position located in a direction
that is perpendicular to the element-forming surface 11c and gets
away from the element-forming surface 11c is defined as "above",
and a position located in a direction opposite to the
above-mentioned direction is defined as "below". Where the layers
included in the head unit 12 are concerned, the surface closer to
the element-forming surface 11c is defined as a "bottom surface,"
and the surface farther from the element-forming surface 11c as a
"top surface." Moreover, X direction, Y direction, Z direction, -X
direction, -Y direction, and -Z direction will be defined as
follows. The X direction is a direction perpendicular to the medium
facing surface 11a and from the medium facing surface 11a to the
rear surface 11b. The Y direction is a direction parallel to the
medium facing surface 11a and the element-forming surface 11c and
from the back side to the front side of FIG. 11. The Z direction is
a direction perpendicular to the element-forming surface 11c and
getting away from the element-forming surface 11c. The -X
direction, the -Y direction, and the -Z direction are opposite to
the X direction, the Y direction, and the Z direction,
respectively. As viewed from the slider 10, the magnetic disk 201
moves in the Z direction. The slider 10 has an air inflow end (a
leading end) at the end of the medium facing surface 11a in the -Z
direction. The slider 10 has an air outflow end (a trailing end) at
the end of the medium facing surface 12a in the Z direction. Track
width direction TW is a direction parallel to the Y direction.
[0070] The light source unit 50 includes a laser diode 60 serving
as a light source for emitting laser light, and a
rectangular-solid-shaped support member 51 that supports the laser
diode 60. The support member 51 is made of, for example, a ceramic
material such as aluminum oxide-titanium carbide
(Al.sub.2O.sub.3--TiC). The support member 51 has a bonding surface
51a, a rear surface 51b on the opposite side from the bonding
surface 51a, and four surfaces that connect the bonding surface 51a
to the rear surface 51b. One of the four surfaces that connect the
bonding surface 51a to the rear surface 51b is a
light-source-mounting surface 51c. The bonding surface 51a is the
surface to be bonded to the rear surface 11b of the slider
substrate 11. The light-source-mounting surface 51c is
perpendicular to the bonding surface 51a and parallel to the
element-forming surface 11c. The laser diode 60 is mounted on the
light-source-mounting surface 51c. The support member 51 may have
the function of a heat sink for dissipating heat generated by the
laser diode 60, in addition to the function of supporting the laser
diode 60.
[0071] As shown in FIG. 11, the head unit 12 includes an insulating
layer 13 disposed on the element-forming surface 11c, and also
includes a read head 14, a write head 16, and a protection layer 17
that are stacked in this order on the insulating layer 13. The
insulating layer 13 and the protection layer 17 are each made of an
insulating material such as Al.sub.2O.sub.3 (hereinafter, also
referred to as alumina).
[0072] The read head 14 includes: a bottom shield layer 21 disposed
on the insulating layer 13; an MR element 22 disposed on the bottom
shield layer 21; a top shield layer 23 disposed on the MR element
22; and an insulating layer 24 disposed between the bottom shield
layer 21 and the top shield layer 23 around the MR element 22. The
bottom shield layer 21 and the top shield layer 23 are each made of
a soft magnetic material. The insulating layer 24 is made of an
insulating material such as alumina.
[0073] An end of the MR element 22 is located in the medium facing
surface 12a. The MR element may be a giant magnetoresistive (GMR)
element or a tunneling magnetoresistive (TMR) element, for example.
The GMR element may be of either the current-in-plane (CIP) type in
which a sense current for use in magnetic signal detection is fed
in a direction nearly parallel to the plane of layers constituting
the GMR element or the current-perpendicular-to-plane (CPP) type in
which the sense current is fed in a direction nearly perpendicular
to the plane of layers constituting the GMR element. If the MR
element 22 is a TMR element or a CPP-type GMR element, the bottom
shield layer 21 and the top shield layer 23 may also function as
electrodes for feeding the sense current to the MR element 22. If
the MR element 22 is a CIP-type GMR element, insulating films are
respectively provided between the MR element 22 and the bottom
shield layer 21 and between the MR element 22 and the top shield
layer 23, and two leads are provided between these insulating films
in order to feed the sense current to the MR element 22.
[0074] The head unit 12 further includes: an insulating layer 25
disposed on the top shield layer 23; a middle shield layer 26
disposed on the insulating layer 25; and an insulating layer 27
disposed on the middle shield layer 26. The middle shield layer 26
has the function of shielding the MR element 22 from a magnetic
field produced in the write head 16. The insulating layers 25 and
27 are each made of an insulating material such as alumina. The
middle shield layer 26 is made of a soft magnetic material. The
insulating layer 25 and the middle shield layer 26 may be
omitted.
[0075] The write head 16 of the present embodiment is for use in
perpendicular magnetic recording. The write head 16 includes: a
bottom yoke layer 28 disposed on the insulating layer 27; a bottom
shield layer 29 disposed on the bottom yoke layer 28 in the
vicinity of the medium facing surface 12a; a coupling layer 42A
disposed on the bottom yoke layer 28 at a position away from the
medium facing surface 12a; and an insulating layer 30 disposed
around the bottom yoke layer 28, the bottom shield layer 29 and the
coupling layer 42A. The bottom yoke layer 28, the bottom shield
layer 29, and the coupling layer 42A are each made of a soft
magnetic material. The insulating layer 30 is made of an insulating
material such as alumina.
[0076] The write head 16 further includes a waveguide that includes
a core 32 and a clad. The clad of the present invention has a clad
layer that constitutes at least part of the clad. In the present
embodiment, the clad has a clad layer 31 and a clad layer 33. Of
these clad layers, the clad layer 33 corresponds to the "clad layer
that constitutes at least part of the clad" according to the
present invention. The clad layer 31 is disposed over the bottom
shield layer 29, the insulating layer 30 and the coupling layer
42A. The core 32 is disposed on the clad layer 31. The clad layer
33 covers the clad layer 31 and the core 32. The core 32 extends in
the direction perpendicular to the medium facing surface 12a (X
direction). The core 32 has an incident end 32a, an end face closer
to the medium facing surface 12a, a top surface, a bottom surface,
and two side surfaces. The end face of the core 32 may be located
in the medium facing surface 12a or away from the medium facing
surface 12a. FIG. 11 shows an example where the end face of the
core 32 is located in the medium facing surface 12a. The core 32
propagates laser light that is emitted from the laser diode 60 and
incident on the incident end 32a.
[0077] The core 32 is made of a dielectric material that transmits
the laser light. Each of the clad layers 31 and 33 is made of a
dielectric material and has a refractive index lower than that of
the core 32. For example, if the laser light has a wavelength of
600 nm and the core 32 is made of Al.sub.2O.sub.3 (refractive index
n=1.63), the clad layers 31 and 33 may be made of SiO.sub.2
(refractive index n=1.46). If the core 32 is made of tantalum oxide
such as Ta.sub.2O.sub.5 (n=2.16), the clad layers 31 and 33 may be
made of SiO.sub.2 (n=1.46) or Al.sub.2O.sub.3 (n=1.63).
[0078] The write head 16 further includes: a plasmon generator 34
disposed above the core 32 near the medium facing surface 12a; and
a magnetic pole 35 disposed at such a position that the plasmon
generator 34 is interposed between the magnetic pole 35 and the
core 32. The plasmon generator 34 is made of a conductive material
such as metal. For example, the plasmon generator 34 may be made of
one element selected from the group consisting of Pd, Pt, Rh, Ir,
Ru, Au, Ag, Cu, and Al, or of an alloy composed of two or more of
these elements. The magnetic pole 35 includes a first layer 351,
and a second layer 352 on the first layer 351. The magnetic pole 35
is made of a soft magnetic material, or a magnetic metal material
in particular. The shapes and locations of the core 32, the plasmon
generator 34 and the magnetic pole 35 will be detailed later.
[0079] The write head 16 further includes a coupling layer 42C
embedded in the clad layer 33 at a position away from the medium
facing surface 12a, and a coupling layer 42D on the coupling layer
42C. The coupling layers 42C and 42D are located above the coupling
layer 42A. The coupling layers 42C and 42D are each made of a soft
magnetic material.
[0080] As shown in FIG. 12, the write head 16 further includes two
coupling portions 42B1 and 42B2 embedded in the clad layers 31 and
33. The coupling portions 42B1 and 42B2 are each made of a soft
magnetic material. The coupling portions 42B1 and 42B2 are located
on opposite sides of the core 32 in the track width direction TW,
each at a distance from the core 32. The bottom surfaces of the
coupling portions 42B1 and 42B2 are in contact with the top surface
of the coupling layer 42A. The top surfaces of the coupling
portions 42B1 and 42B2 are in contact with the bottom surface of
the coupling layer 42C.
[0081] The write head 16 further includes: an insulating layer 37
disposed around the second layer 352 and the coupling layer 42D on
the clad layer 33; an insulating layer 38 disposed on the
insulating layer 37; a coupling layer 36 disposed on the second
layer 352; and a coupling layer 42E disposed on the coupling layer
42D.
[0082] The write head 16 further includes a plurality of first coil
elements 40A disposed on the insulating layer 38, and an insulating
layer 39 disposed around the coupling layers 36 and 42E and the
first coil elements 40A. The first coil elements 40A are arranged
to align in the X direction. Although not shown, the first coil
elements 40A each have a main part that extends in the track width
direction TW (Y direction). The first coil elements 40A are each
made of a conductive material such as copper. The coupling layers
36 and 42E are each made of a soft magnetic material. The
insulating layers 37, 38, and 39 are made of alumina, for
example.
[0083] The write head 16 further includes an insulating layer 41
disposed to cover the first coil elements 40A, a top yoke layer 43
disposed over the coupling layers 36 and 42E and the insulating
layer 41, and an insulating layer 44 disposed around the top yoke
layer 43. The top yoke layer 43 is in contact with the top surface
of the coupling layer 36 at a position near the medium facing
surface 12a, and in contact with the top surface of the coupling
layer 42E at a position away from the medium facing surface 12a.
The top yoke layer 43 is made of a soft magnetic material. The
insulating layers 41 and 44 are each made of an insulating material
such as alumina. The write head 16 further includes an insulating
layer 45 disposed over the top yoke layer 43 and the insulating
layer 44, and a plurality of second coil elements 40B disposed on
the insulating layer 45. The insulating layer 45 is made of an
insulating material such as alumina.
[0084] FIG. 12 shows the second coil elements 40B. The second coil
elements 40B are arranged to align in the X direction. The second
coil elements 40B each have a main part that extends in the track
width direction TW (Y direction). The second coil elements 40B are
each made of a conductive material such as copper.
[0085] Although not shown, the thermally-assisted magnetic
recording head 1 further includes a plurality of connecting
portions. The plurality of connecting portions connect the
plurality of first coil elements 40A to the plurality of second
coil elements 40B so as to form a coil 40 wound around the top yoke
layer 43 helically. The plurality of connecting portions are
provided to penetrate the insulating layers 41, 44, and 45. The
connecting portions are each made of a conductive material such as
copper.
[0086] In the write head 16, the bottom shield layer 29, the bottom
yoke layer 28, the coupling layer 42A, the coupling portions 42B1
and 42B2, the coupling layers 42C, 42D and 42E, the top yoke layer
43, the coupling layer 36, and the magnetic pole 35 form a magnetic
path for passing a magnetic flux corresponding to the magnetic
field produced by the coil 40. The magnetic pole 35 has an end face
located in the medium facing surface 12a, allows the magnetic flux
corresponding to the magnetic field produced by the coil 40 to
pass, and produces a write magnetic field for writing data on the
magnetic disk 201 by means of the perpendicular magnetic recording
system. The bottom shield layer 29 takes in a magnetic flux that is
generated from the end face of the magnetic pole 35 and that
expands in directions other than the direction perpendicular to the
plane of the magnetic disk 201, and thereby prevents the magnetic
flux from reaching the magnetic disk 201.
[0087] As shown in FIG. 11, the protection layer 17 is disposed to
cover the write head 16. As shown in FIG. 10, the head unit 12
further includes a pair of terminals 18 that are disposed on the
top surface of the protection layer 17 and electrically connected
to the MR element 22, and another pair of terminals 19 that are
disposed on the top surface of the protection layer 17 and
electrically connected to the coil 40. These terminals 18 and 19
are electrically connected to the plurality of pad-shaped terminals
of the wiring member 224 shown in FIG. 9.
[0088] The laser diode 60 may be a laser diode of InP type, GaAs
type, GaN type or the like that is commonly used for such
applications as communications, optical disc storage and material
analysis. The laser diode 60 may emit laser light of any wavelength
within the range of, for example, 375 nm to 1.7 .mu.m.
Specifically, the laser diode 60 may be an InGaAsP/InP quaternary
mixed crystal laser diode having an emittable wavelength range of
1.2 to 1.67 .mu.m, for example.
[0089] As shown in FIG. 11, the laser diode 60 has a multilayer
structure including a lower electrode 61, an active layer 62, and
an upper electrode 63. A reflecting layer 64 made of, for example,
SiO.sub.2 or Al.sub.2O.sub.3, is formed on two cleavage planes of
the multilayer structure so as to excite oscillation by total
reflection of light. The reflecting layer 64 has an opening for
emitting laser light in the position of the active layer 62
including an emission center 62a. The laser diode 60 has a
thickness T.sub.LA of around 60 to 200 .mu.m, for example.
[0090] The light source unit 50 further includes a terminal 52
disposed on the light-source-mounting surface 51c and electrically
connected to the lower electrode 61, and a terminal 53 disposed on
the light-source-mounting surface 51c and electrically connected to
the upper electrode 63. These terminals 52 and 53 are electrically
connected to the plurality of pad-shaped terminals of the wiring
member 224 shown in FIG. 9. When a predetermined voltage is applied
to the laser diode 60 through the terminals 52 and 53, laser light
is emitted from the emission center 62a of the laser diode 60. The
laser light to be emitted from the laser diode 60 is preferably
TM-mode polarized light whose electric field oscillates in a
direction perpendicular to the plane of the active layer 62.
[0091] The laser diode 60 can be driven by a power supply inside
the magnetic disk drive. The magnetic disk drive usually includes a
power supply that generates a voltage of 2 V or so, for example.
This supply voltage is sufficient to drive the laser diode 60. The
laser diode 60 has a power consumption of, for example, several
tens of milliwatts or so, which can be adequately covered by the
power supply in the magnetic disk drive.
[0092] The light source unit 50 is fixed to the slider 10 by
bonding the bonding surface 51a of the support member 51 to the
rear surface 11b of the slider substrate 11, as shown in FIG. 11.
The laser diode 60 and the core 32 are positioned so that the laser
light emitted from the laser diode 60 will be incident on the
incident end 32a of the core 32.
[0093] The shapes and locations of the core 32, the plasmon
generator 34, and the magnetic pole 35 will now be described in
detail with reference to FIG. 1 to FIG. 6. FIG. 1 is a perspective
view showing the core 32, the plasmon generator 34, and the
magnetic pole 35. FIG. 2 is an exploded perspective view of the
plasmon generator 34 and the magnetic pole 35 shown in FIG. 1. FIG.
3 is a perspective view showing the core 32 and the plasmon
generator 34. FIG. 4 is a front view showing a part of the medium
facing surface 12a of the head unit 12. FIG. 5 is an enlarged front
view of a part of the core 32 and the plasmon generator 34 shown in
FIG. 4. FIG. 6 is a cross-sectional view showing the core 32, the
plasmon generator 34, and the magnetic pole 35. FIG. 7 is a plan
view of the plasmon generator 34.
[0094] Aside from the incident end 32a shown in FIG. 11, the core
32 further has: an end face 32b that is closer to the medium facing
surface 12a; an evanescent light generating surface 32c which is a
top surface; a bottom surface 32d; and two side surfaces 32e and
32f, as shown in FIG. 3. The evanescent light generating surface
32c generates evanescent light based on the light propagated
through the core 32. While FIG. 1 to FIG. 6 show an example where
the end face 32b is located in the medium facing surface 12a, the
end face 32b may be located away from the medium facing surface
12a. The end face 32b includes a top side 32b1, a bottom side 32b2,
and two sides 32b3 and 32b4 connecting the top side and the bottom
side to each other. In the vicinity of the plasmon generator 34A,
the core 32 has a trapezoidal shape in cross section parallel to
the medium facing surface 12a, the trapezoidal shape being such
that the top side is shorter than the bottom side, for example. In
such a case, the end face 32b has a trapezoidal shape with its top
side 32b1 shorter than the bottom side 32b2. The two sides 32b3 and
32b4 form the same angle with respect to the direction
perpendicular to the top side 32b1.
[0095] As shown in FIG. 4, the clad layer 33 has a top surface 33a
that is located above the core 32, and a groove 33b that opens in
the top surface 33a and is located above the core 32. The groove
33b has a shape corresponding to the plasmon generator 34. The
groove 33b includes a V-shaped groove portion that has an end
located in the medium facing surface 12a. The V-shaped groove
portion extends in the direction perpendicular to the medium facing
surface 12a (X direction). The V-shaped groove portion is V-shaped
in cross section parallel to the medium facing surface 12a. The
V-shaped groove portion has first and second sidewalls 33b1 and
33b2 that decrease in distance from each other with increasing
distance from the top surface 33a of the clad layer 33.
[0096] As shown in FIG. 4, the thermally-assisted magnetic
recording head 1 further includes a dielectric film 72 disposed at
least in the V-shaped groove portion of the groove 33b. The groove
33b and the dielectric film 72 constitute an accommodating part 70
for accommodating the plasmon generator 34. As will be described
later, the dielectric film 72 is intended for determining the shape
of the plasmon generator 34. The dielectric film 72 is made of a
dielectric material and has a refractive index lower than that of
the core 32. The dielectric film 72 may be made of the same
material as that of the clad layer 33.
[0097] The dielectric film 72 includes a first film portion 72a
that adheres to the first sidewall 33b1, and a second film portion
72b that adheres to the second sidewall 33b2. The first film
portion 72a includes an upper part 72a1 and a lower part 72a2 that
are continuous with each other. The second film portion 72b
includes an upper part 72b1 and a lower part 72b2 that are
continuous with each other. In FIG. 4, the border between the upper
part 72a1 and the lower part 72a2 and the border between the upper
part 72b1 and the lower part 72b2 are shown by respective dotted
lines. In the first film portion 72a, the lower part 72a2 has a
thickness smaller than that of the upper part 72a1 in the direction
perpendicular to the first sidewall 33b1. In the second film
portion 72b, the lower part 72b2 has a thickness smaller than that
of the upper part 72b1 in the direction perpendicular to the second
sidewall 33b2.
[0098] As shown in FIG. 2 and FIG. 3, the plasmon generator 34 has
a V-shaped portion 34A that has an end face located in the medium
facing surface 12a. The V-shaped portion 34A extends in the
direction perpendicular to the medium facing surface 12a (X
direction). The V-shaped portion 34A is V-shaped in cross section
parallel to the medium facing surface 12a. The V-shaped groove
portion of the groove 33b described above is to accommodate the
V-shaped portion 34A. The V-shaped portion 34A is accommodated in
the V-shaped groove portion so that the first film portion 72a is
interposed between the first sidewall 33b1 and the V-shaped portion
34A and the second film portion 72b is interposed between the
second sidewall 33b2 and the V-shaped portion 34A.
[0099] The plasmon generator 34 further has a second portion 34B
and a third portion 34C. The second portion 34B is located farther
from the medium facing surface 12a than is the V-shaped portion
34A, such that the second portion 34B is continuous with the
V-shaped portion 34A. The third portion 34C is located farther from
the medium facing surface 12a than is the second portion 34B, such
that the third portion 34C is continuous with the second portion
34B. In FIG. 3 and FIG. 7, the border between the second portion
34B and the third portion 34C is shown by a chain double-dashed
line.
[0100] The second portion 34B has: a bottom part 34B1 that is
shaped like a plate and faces the evanescent light generating
surface 32c; and two sidewall parts 34B2 and 34B3 that are each
shaped like a plate. The sidewall parts 34B2 and 34B3 are located
farther from the evanescent light generating surface 32c than is
the bottom part 34B1, and are connected to opposite ends of the
bottom part 34B1 in the direction parallel to the medium facing
surface 12a and the evanescent light generating surface 32c (Y
direction).
[0101] The bottom part 34B1 has a width that decreases with
decreasing distance to the medium facing surface 12a, the width
being in the direction parallel to the medium facing surface 12a
and the evanescent light generating surface 32c (Y direction). The
bottom part 34B1 has an end closer to the medium facing surface
12a. At this end of the bottom part 34B1, the bottom part 34B1 has
a zero width and the respective bottom ends of the sidewall parts
34B2 and 34B3 are in contact with each other.
[0102] The distance between the two sidewall parts 34B2 and 34B3 in
the direction parallel to the medium facing surface 12a and the
evanescent light generating surface 32c (Y direction) increases
with increasing distance from the evanescent light generating
surface 32c, and decreases with decreasing distance to the medium
facing surface 12a.
[0103] The third portion 34C has: a bottom part 34C1 that is
continuous with the bottom part 34B1 of the second portion 34B; a
sidewall part 34C2 that is continuous with the sidewall part 34B2
of the second portion 34B; a sidewall part 34C3 that is continuous
with the sidewall part 34B3 of the second portion 34B; and a wall
part 34C4 that connects respective ends of the bottom part 34C1 and
the sidewall parts 34C2 and 34C3 to each other, the ends being
farther from the medium facing surface 12a. The bottom part 34C1
has a constant width in the direction parallel to the medium facing
surface 12a and the evanescent light generating surface 32c (Y
direction) regardless of the distance from the medium facing
surface 12a. Note that the third portion 34C need not necessarily
have the wall part 34C4.
[0104] The distance between the two sidewall parts 34C2 and 34C3 in
the direction parallel to the medium facing surface 12a and the
evanescent light generating surface 32c (Y direction) increases
with increasing distance from the evanescent light generating
surface 32c, but does not change according to the distance from the
medium facing surface 12a.
[0105] As shown in FIG. 3, the V-shaped portion 34A, the second
portion 34B, and the third portion 34C of the plasmon generator 34
form inside a space for accommodating the first layer 351 of the
magnetic pole 35.
[0106] The plasmon generator 34 has an outer surface including a
plurality of portions described below, and has a near-field light
generating part 34g located in the medium facing surface 12a. As
shown in FIG. 2, the outer surface of the plasmon generator 34
includes a plasmon exciting part 341 that faces the evanescent
light generating surface 32c of the core 32 with a predetermined
distance therebetween. The near-field light generating part 34g
lies at an end of the plasmon exciting part 341.
[0107] As shown in FIG. 6, the part of the clad layer 33 interposed
between the evanescent light generating surface 32c and the plasmon
exciting part 341 forms a buffer part 33A having a refractive index
lower than that of the core 32.
[0108] As shown in FIG. 2, the plasmon exciting part 341 includes a
propagative edge 341a and a flat surface part 341b. The propagative
edge 341a is formed by the bottom end of the V-shaped portion 34A.
The flat surface part 341b includes a width changing portion 341b1
formed by the bottom surface of the bottom part 34B1 of the second
portion 34B, and a constant width portion 341b2 formed by the
bottom surface of the bottom part 34C1 of the third portion 34C. In
FIG. 2, the border between the width changing portion 341b1 and the
constant width portion 341b2 is shown by a chain double-dashed
line.
[0109] The width changing portion 341b1 has a width that decreases
with decreasing distance to the medium facing surface 12a, the
width being in the direction parallel to the medium facing surface
12a and the evanescent light generating surface 32c (Y direction).
The width changing portion 341b1 has a front end part that is
closer to the medium facing surface 12a, and two sides that are
opposite in the direction of the width (Y direction). The front end
part of the width changing portion 341b1 is located at a distance
from the medium facing surface 12a. The propagative edge 341a
connects the front end part of the width changing portion 341b1 to
the near-field light generating part 34g. The angle that one of the
two sides of the width changing portion 341b1 forms with respect to
the direction perpendicular to the medium facing surface 12a (X
direction) is equal to the angle that the other of the two sides
forms with respect to the direction perpendicular to the medium
facing surface 12a (X direction). This angle falls within the range
of 3 to 50 degrees, and preferably within the range of 10 to 25
degrees.
[0110] The constant width portion 341b2 is located farther from the
medium facing surface 12a than is the width changing portion 341b1,
such that the constant width portion 341b2 is continuous with the
width changing portion 341b1. The constant width portion 341b2 has
a constant width in the direction parallel to the medium facing
surface 12a and the evanescent light generating surface 32c (Y
direction) regardless of the distance from the medium facing
surface 12a.
[0111] As shown in FIG. 2 and FIG. 3, the outer surface of the
plasmon generator 34 further includes a first inclined surface 342
and a second inclined surface 343 that are each connected to the
plasmon exciting part 341. The first and second inclined surfaces
342 and 343 increase in distance from each other with increasing
distance from the plasmon exciting part 341. The plasmon exciting
part 341 connects respective ends of the inclined surfaces 342 and
343 to each other, the ends being closer to the evanescent light
generating surface 32c.
[0112] As shown in FIG. 2, the first inclined surface 342 includes
an inclined surface 342a that is included in the V-shaped portion
34A, an inclined surface 342b that is included in the second
portion 34B, and an inclined surface 342c that is included in the
third portion 34C. As shown in FIG. 3, the second inclined surface
343 includes an inclined surface 343a that is included in the
V-shaped portion 34A, an inclined surface 343b that is included in
the second portion 34B, and an inclined surface 343c that is
included in the third portion 34C.
[0113] The inclined surfaces 342a and 343a are formed by the
surfaces of the V-shaped portion 34A that lie on opposite sides in
the direction parallel to the medium facing surface 12a and the
evanescent light generating surface 32c (Y direction). The
propagative edge 341a connects respective ends of the inclined
surfaces 342a and 343a to each other, the respective ends being
closer to the evanescent light generating surface 32c. In a cross
section parallel to the medium facing surface 12a, the propagative
edge 341a is shaped like a pointed edge in a macroscopic view, but
has an arc shape in a microscopic view.
[0114] The inclined surfaces 342b and 343b are formed by the
respective surfaces of the sidewall parts 34B2 and 34B3 of the
second portion 34B that lie on opposite sides in the direction
parallel to the medium facing surface 12a and the evanescent light
generating surface 32c (Y direction). The width changing portion
341b1 connects respective ends of the inclined surfaces 342b and
343b to each other, the respective ends being closer to the
evanescent light generating surface 32c.
[0115] The inclined surfaces 342c and 343c are formed by the
respective surfaces of the sidewall parts 34C2 and 34C3 of the
third portion 34C that lie on opposite sides in the direction
parallel to the medium facing surface 12a and the evanescent light
generating surface 32c (Y direction). The constant width portion
341b2 connects respective ends of the inclined surfaces 342c and
343c to each other, the respective ends being closer to the
evanescent light generating surface 32c.
[0116] As shown in FIG. 5, the inclined surface 342a includes an
upper part 342a1 and a lower part 342a2 that are continuous with
each other. The inclined surface 343a includes an upper part 343a1
and a lower part 343a2 that are continuous with each other. Here,
the angles that the upper parts 342a1 and 343a1 and the lower parts
342a2 and 343a2 form with respect to the direction perpendicular to
the evanescent light generating surface 32c will be referred to as
their respective inclination angles. The upper parts 342a1 and
343a1 have the same inclination angle. This angle will hereinafter
be represented by the symbol .theta..sub.1. The lower parts 342a2
and 343a2 have the same inclination angle. This angle will
hereinafter be represented by the symbol .theta..sub.2. The angle
.theta..sub.2 is smaller than the angle .theta..sub.1.
[0117] The angle formed between the upper part 342a1 and the upper
part 343a1 is twice the inclination angle .theta..sub.1 of each of
the upper parts 342a1 and 343a1, i.e., 201. The angle formed
between the lower part 342a2 and the lower part 343a2 is twice the
inclination angle .theta..sub.2 of each of the lower parts 342a2
and 343a2, i.e., 202. The angle 2.theta..sub.2 is smaller than the
angle 2.theta..sub.1.
[0118] The wave number of the surface plasmons to be excited on the
plasmon generator 34 varies according to the shape of the plasmon
generator 34. The shape of the plasmon generator 34 depends largely
on the magnitude of the angle .theta..sub.1 in particular, between
the two types of angles .theta..sub.1 and .theta..sub.2. Between
the two types of angles .theta..sub.1 and .theta..sub.2, the angle
.theta..sub.1 in particular is a parameter that affects the wave
number of the surface plasmons to be excited on the plasmon
generator 34. The angle .theta..sub.2 is a parameter that affects
the spot diameter of the near-field light to be generated by the
near-field light generating part 34g. The angle .theta..sub.1
preferably falls within the range of 15 to 60 degrees. The angle
.theta..sub.2 preferably falls within the range of 10 to 20
degrees.
[0119] As shown in FIG. 4, the outer surface of the plasmon
generator 34 further includes a front end face 344 that is located
in the medium facing surface 12a and connected to the first and
second inclined surfaces 342 and 343. The front end face 344 is
also the end face of the V-shaped portion 34A. The front end face
344 has first and second portions 344a and 344b that are connected
to each other into a V-shape. The front end face 344 further has a
bottom end 344c that is closer to the evanescent light generating
surface 32c. The bottom end 344c forms the near-field light
generating part 34g. The bottom end 344c is shaped like a pointed
edge in a macroscopic view, but has an arc shape in a microscopic
view.
[0120] As shown in FIG. 5, the first portion 344a includes a first
side 345a that lies at an end of the first inclined surface 342
(inclined surface 342a). The second portion 344b includes a second
side 345b that lies at an end of the second inclined surface 343
(inclined surface 343a). The first and second sides 345a and 345b
are each connected to the bottom end 344c.
[0121] The first side 345a includes an upper part 345a1 and a lower
part 345a2 that are continuous with each other. The second side
345b includes an upper part 345b1 and a lower part 345b2 that are
continuous with each other. In FIG. 5, the reference numeral 345a3
designates the border between the upper part 345a1 and the lower
part 345a2, and the reference numeral 345b3 designates the border
between the upper part 345b1 and the lower part 345b2. The angles
that the upper parts 345a1 and 345b1 and the lower parts 345a2 and
345b2 form with respect to the direction perpendicular to the
evanescent light generating surface 32c will be referred to as
their respective inclination angles.
[0122] The inclination angle of the upper part 345a1 of the first
side 345a is equal to the inclination angle .theta..sub.1 of the
upper part 342a1 of the inclined surface 342a. The inclination
angle of the upper part 345b1 of the second side 345b is equal to
the inclination angle .theta..sub.1 of the upper part 343a1 of the
inclined surface 343a. The inclination angles of the upper parts
345a1 and 345b1 are therefore equal.
[0123] The inclination angle of the lower part 345a2 of the first
side 345a is equal to the inclination angle .theta..sub.2 of the
lower part 342a2 of the inclined surface 342a. The inclination
angle of the lower part 345b2 of the second side 345b is equal to
the inclination angle .theta..sub.2 of the lower part 343a2 of the
inclined surface 343a. The inclination angles of the lower parts
345a2 and 345b2 are therefore equal.
[0124] The angle formed between the upper part 345a1 and the upper
part 345b1 is twice the inclination angle .theta..sub.1 of each of
the upper parts 345a1 and 345b1, i.e., 201. The angle formed
between the lower part 345a2 and the lower part 345b2 is twice the
inclination angle .theta..sub.2 of each of the lower parts 345a2
and 345b2, i.e., 2.theta..sub.2. The angle 2.theta..sub.2 is
smaller than the angle 2.theta..sub.1.
[0125] As shown in FIG. 2 and FIG. 4, the magnetic pole 35 has an
end face 35a located in the medium facing surface 12a. The end face
35a includes an end face 35a1 of the first layer 351 located in the
medium facing surface 12a and an end face 35a2 of the second layer
352 located in the medium facing surface 12a.
[0126] The first layer 351 of the magnetic pole 35 is accommodated
in the space formed by the V-shaped portion 34A, the second portion
34B, and the third portion 34C of the plasmon generator 34. The
first layer 351 includes a first portion 351A, a second portion
351B, and a third portion 351C. The first portion 351A is
accommodated in the space formed by the V-shaped portion 34A. The
second portion 351B is accommodated in the space formed by the
second portion 34B (the bottom part 34B1 and the sidewall parts
34B2 and 34B3). The third portion 351C is accommodated in the space
formed by the third portion 34C (the bottom part 34C1 and the
sidewall parts 34C2 and 34C3).
[0127] The first portion 351A is generally triangular-prism-shaped.
The first portion 351A is accommodated in the V-shaped portion 34A
and is in contact with the V-shaped portion 34A. The first portion
351A has a constant width in the direction parallel to the medium
facing surface 12a and the evanescent light generating surface 32c
(Y direction) regardless of the distance from the medium facing
surface 12a. The end face of the first portion 351A located in the
medium facing surface 12a, i.e., the end face 35a1 of the first
layer 351 located in the medium facing surface 12a, is generally
triangle-shaped and is interposed between the two portions 344a and
344b of the front end face 344 of the plasmon generator 34. The end
face 35a1 has a tip 35c located at its bottom end.
[0128] The second portion 351B is interposed between the two
sidewall parts 34B2 and 34B3 of the second portion 34B of the
plasmon generator 34, and is in contact with the bottom part 34B1
and the two sidewall parts 34B2 and 34B3. The width of the second
portion 351B in the direction parallel to the medium facing surface
12a and the evanescent light generating surface 32c (Y direction)
increases with increasing distance from the evanescent light
generating surface 32c, and decreases with decreasing distance to
the medium facing surface 12a.
[0129] The third portion 351C is interposed between the two
sidewall parts 34C2 and 34C3 of the third portion 34C of the
plasmon generator 34, and is in contact with the bottom part 34C1
and the two sidewall parts 34C2 and 34C3. The width of the third
portion 351C in the direction parallel to the medium facing surface
12a and the evanescent light generating surface 32c (Y direction)
increases with increasing distance from the evanescent light
generating surface 32c, but does not change according to the
distance from the medium facing surface 12a.
[0130] The second layer 352 of the magnetic pole 35 has a bottom
surface that is in contact with the top surface of the first layer
351 and the respective top end surfaces of the V-shaped portion
34A, the second portion 34B and the third portion 34C of the
plasmon generator 34.
[0131] The plasmon generator 34 need not necessarily have the third
portion 34C. If the plasmon generator 34 does not have the third
portion 34C, the first layer 351 of the magnetic pole 35 does not
have the third portion 351C.
[0132] As shown in FIG. 3, the width of the evanescent light
generating surface 32c in the track width direction TW (Y
direction) in the vicinity of the plasmon generator 34 will be
represented by the symbol W.sub.WG. The thickness (dimension in the
Z direction) of the core 32 in the vicinity of the plasmon
generator 34 will be represented by the symbol T.sub.WG. W.sub.WG
falls within the range of 0.3 to 100 .nu.m, for example. T.sub.WG
falls within the range of 0.1 to 4 .mu.m, for example. As shown in
FIG. 12, the core 32 excluding the part in the vicinity of the
plasmon generator 34 may have a width greater than W.sub.WG. As
shown in FIG. 5, the angle that each of the two sides 32b3 and 32b4
of the end face 32b of the core 32 forms with respect to the
direction perpendicular to the top side 32b1 will be represented by
the symbol .theta..sub.WG. The angle .theta..sub.WG is 5 degrees,
for example
[0133] As shown in FIG. 3 and FIG. 5, the dimension of the plasmon
generator 34 in the track width direction TW (Y direction) at the
medium facing surface 12a will be represented by the symbol
W.sub.PG. The dimension of the plasmon generator 34 in the Z
direction at the medium facing surface 12a will be represented by
the symbol T.sub.PG. Both W.sub.PG and T.sub.PG are sufficiently
smaller than the wavelength of the laser light to be propagated
through the core 32. As shown in FIG. 5, the distance between a
virtual straight line L and the bottom end 344c will be represented
by the symbol T.sub.PG2. The virtual straight line L passes through
the border 345a3 between the upper part 345a1 and the lower part
345a2 of the first side 345a and the border 345b3 between the upper
part 345b1 and the lower part 345b2 of the second side 345b.
T.sub.PG2 is smaller than T.sub.PG. T.sub.PG2 preferably falls
within the range of 10 to 25 nm. The reason will be detailed later.
As shown in FIG. 7, the dimension of the third portion 34C of the
plasmon generator 34 in the track width direction TW (Y direction)
will be represented by the symbol W.sub.PGL. W.sub.PGL falls within
the range of 350 to 450 nm, for example.
[0134] When T.sub.PG2 is sufficiently smaller than T.sub.PG, the
relationship between W.sub.PG, T.sub.PG, and .theta..sub.1 is
generally expressed by the following equation:
W.sub.PG=2.times.T.sub.PG.times.tan .theta..sub.1.
[0135] For example, when .theta..sub.1 is 28 degrees and T.sub.PG
is in the range of 50 to 250 nm, W.sub.PG falls within the range of
53 to 266 nm.
[0136] As shown in FIG. 6 and FIG. 7, the length of the plasmon
generator 34 in the X direction will be represented by the symbol
H.sub.PG. H.sub.PG falls within the range of 0.6 to 4.0 .mu.m, for
example. The lengths of the V-shaped portion 34A, the second
portion 34B, and the third portion 34C of the plasmon generator 34
in the X direction will be represented by the symbols H.sub.PGA,
H.sub.PGB, and H.sub.PGC, respectively. H.sub.PGA falls within the
range of 0.01 to 1.0 .mu.m, for example. H.sub.PGB falls within the
range of 0.1 to 4.0 .mu.m, for example. H.sub.PGC falls within the
range of 0.0 to 3.9 .mu.m, for example.
[0137] As shown in FIG. 6, the X-direction length of a portion of
the plasmon exciting part 341 of the plasmon generator 34, the
portion facing the evanescent light generating surface 32c, will be
represented by the symbol H.sub.BF. The distance between the
plasmon exciting part 341 and the evanescent light generating
surface 32c will be represented by the symbol T.sub.BF. Both
H.sub.BF and T.sub.BF are important parameters in achieving
appropriate excitation and propagation of surface plasmons.
H.sub.BF preferably falls within the range of 0.6 to 4.0 .mu.m, and
is preferably greater than the wavelength of the laser light to be
propagated through the core 32. In the example shown in FIG. 6, the
end face 32b of the core 32 is located in the medium facing surface
12a, so that H.sub.BF is equal to H.sub.PG. T.sub.BF preferably
falls within the range of 10 to 100 nm. As shown in FIG. 5, the
distance between the bottom end 344c of the front end face 344 of
the plasmon generator 34 and the end face 32b of the core 32 is
equal to T.sub.BF.
[0138] As shown in FIG. 5, the distance between the bottom end 344c
of the front end face 344 of the plasmon generator 34 and the tip
35c (see FIG. 4) of the end face 35a1 of the first layer 351 of the
magnetic pole 35 will be represented by the symbol D. D preferably
falls within the range of 10 to 100 nm.
[0139] Reference is now made to FIG. 6 to describe the principle of
generation of near-field light in the present embodiment and the
principle of thermally-assisted magnetic recording using the
near-field light. Laser light 46 emitted from the laser diode 60 is
propagated through the core 32 of the waveguide to reach the
vicinity of the plasmon generator 34. Here, the laser light 46 is
totally reflected at the evanescent light generating surface 32c
which is the interface between the core 32 and the buffer part 33A.
This generates evanescent light 47 permeating into the buffer part
33A. Then, the evanescent light 47 and fluctuations of charges on
the plasmon exciting part 341 of the outer surface of the plasmon
generator 34 are coupled with each other to induce a surface
plasmon polariton mode. In this way, surface plasmons are excited
on the plasmon exciting part 341 through coupling with the
evanescent light 47 generated from the evanescent light generating
surface 32c.
[0140] The plasmon exciting part 341 includes the propagative edge
341a and the flat surface part 341b. The flat surface part 341b
includes the width changing portion 341b1. The width of the width
changing portion 341b1 in the direction parallel to the medium
facing surface 12a and the evanescent light generating surface 32c
(Y direction) decreases with decreasing distance to the medium
facing surface 12a. The surface plasmons excited on the flat
surface part 341b are gradually transformed into edge plasmons,
which are surface plasmons to propagate along the two sides of the
width changing portion 341b1 that are opposite in the direction of
the width (Y direction), while propagating over the width changing
portion 341b1. The surface plasmons (including edge plasmons)
propagating over the width changing portion 341b1 reach the
propagative edge 341a, and are transformed into edge plasmons to
propagate along the propagative edge 341a. The propagative edge
341a propagates the edge plasmons that are based on the surface
plasmons excited on the flat surface part 341b, and the edge
plasmons that are excited on the propagative edge 341a. Those edge
plasmons are propagated along the propagative edge 341a to the
near-field light generating part 34g.
[0141] The foregoing edge plasmons concentrate at the near-field
light generating part 34g, and near-field light 48 occurs from the
near-field light generating part 34g based on the edge plasmons.
The near-field light 48 is projected toward the magnetic disk 201,
reaches the surface of the magnetic disk 201, and heats a part of
the magnetic recording layer of the magnetic disk 201. This lowers
the coercivity of the part of the magnetic recording layer. In
thermally-assisted magnetic recording, the part of the magnetic
recording layer with the lowered coercivity is subjected to a write
magnetic field produced by the magnetic pole 35 for data
writing.
[0142] In the width changing portion 341b1, the propagating
plasmons increase in electric field intensity. This is presumably
based on the following first and second principles. Initially, a
description will be given of the first principle. The wave number
of the surface plasmons propagating over the width changing portion
341b1 increases as the width of the width changing portion 341b1
decreases. As the wave number of the surface plasmons increases,
the speed of travel of the surface plasmons decreases. This
consequently increases the energy density of the surface plasmons
and enhances the electric field intensity of the surface
plasmons.
[0143] Next, a description will be given of the second principle.
When the surface plasmons propagate over the width changing portion
341b1, some of the surface plasmons impinge on the two sides of the
width changing portion 341b1 that are opposite in the direction of
the width (Y direction) to scatter, thereby generating a plurality
of plasmons with different wave numbers. Some of the plurality of
plasmons thus generated are transformed into edge plasmons having a
wave number higher than that of the surface plasmons propagating
over a flat surface. In this way, the surface plasmons are
gradually transformed into the edge plasmons to propagate along the
two sides, whereby the edge plasmons gradually increase in electric
field intensity. As compared with the surface plasmons propagating
over a flat surface, the edge plasmons are higher in wave number
and lower in speed of travel. Consequently, the transformation of
the surface plasmons into the edge plasmons increases the energy
density of the plasmons. In the width changing portion 341b1, the
foregoing transformation of the surface plasmons into the edge
plasmons is accompanied by the generation of new surface plasmons
based on the evanescent light occurring from the evanescent light
generating surface 32c. The new surface plasmons are also
transformed into edge plasmons. As a result, the edge plasmons
increase in electric field intensity. Those edge plasmons are
transformed into edge plasmons that propagate over the propagation
edge 341a. This generates the edge plasmons that are higher in
electric field intensity than the surface plasmons originally
generated.
[0144] In the width changing portion 341b1, the surface plasmons
propagating over the flat surface and the edge plasmons having a
wave number higher than that of the surface plasmons coexist. It
can be considered that both the surface plasmons and the edge
plasmons increase in electric field intensity in the width changing
portion 341b1 based on the first and second principles described
above. In the width changing portion 341b1, the electric field
intensity of the plasmons can thus be enhanced as compared with a
case where either one of the first principle and the second
principle is in operation.
[0145] Reference is now made to FIG. 13 to describe the circuit
configuration of the control circuit 230 shown in FIG. 8 and the
operation of the thermally-assisted magnetic recording head 1. The
control circuit 230 includes a control LSI (large scale integrated
circuit) 100, a ROM (read only memory) 101 connected to the control
LSI 100, a write gate 111 connected to the control LSI 100, and a
write circuit 112 connected to the write gate 111 and the coil
40.
[0146] The control circuit 230 further includes a constant current
circuit 121 connected to the MR element 22 and the control LSI 100,
an amplifier 122 connected to the MR element 22, and a demodulator
circuit 123 connected to an output of the amplifier 122 and the
control LSI 100.
[0147] The control circuit 230 further includes a laser control
circuit 131 connected to the laser diode 60 and the control LSI
100, and a temperature detector 132 connected to the control LSI
100.
[0148] The control LSI 100 supplies write data and a write control
signal to the write gate 111. The control LSI 100 supplies a read
control signal to the constant current circuit 121 and the
demodulator circuit 123, and receives read data output from the
demodulator circuit 123. The control LSI 100 supplies a laser
ON/OFF signal and an operating current control signal to the laser
control circuit 131. The temperature detector 132 detects the
temperature of the magnetic recording layer of the magnetic disk
201, and supplies this temperature information to the control LSI
100. The ROM 101 contains a control table and the like for
controlling the value of the operating current to be supplied to
the laser diode 60.
[0149] In a write operation, the control LSI 100 supplies write
data to the write gate 111. The write gate 111 supplies the write
data to the write circuit 112 only when the write control signal
indicates a write operation. According to the write data, the write
circuit 112 passes a write current through the coil 40.
Consequently, the magnetic pole 35 produces a write magnetic field
and data is written on the magnetic recording layer of the magnetic
disk 201 through the use of the write magnetic field.
[0150] In a read operation, the constant current circuit 121
supplies a certain sense current to the MR element 22 only when the
read control signal indicates a read operation. The output voltage
of the MR element 22 is amplified by the amplifier 122 and input to
the demodulator circuit 123. When the read control signal indicates
a read operation, the demodulator circuit 123 demodulates the
output of the amplifier 122 to generate read data, and supplies the
read data to the control LSI 100.
[0151] The laser control circuit 131 controls the supply of the
operating current to the laser diode 60 on the basis of the laser
ON/OFF signal, and also controls the value of the operating current
to be supplied to the laser diode 60 on the basis of the operating
current control signal. When the laser ON/OFF signal indicates an
ON operation, the laser control circuit 131 exercises control so
that an operating current at or above an oscillation threshold is
supplied to the laser diode 60. Consequently, the laser diode 60
emits laser light, and the laser light is propagated through the
core 32. According to the principle of generation of near-field
light described previously, the near-field light 48 occurs from the
near-field light generating part 34g of the plasmon generator 34.
The near-field light 48 heats a part of the magnetic recording
layer of the magnetic disk 201, thereby lowering the coercivity of
that part. When writing, the part of the magnetic recording layer
with the lowered coercivity is subjected to the write magnetic
field produced by the magnetic pole 35 for performing data
writing.
[0152] On the basis of such factors as the temperature of the
magnetic recording layer of the magnetic disk 201 measured by the
temperature detector 132, the control LSI 100 consults the control
table stored in the ROM 101 to determine the value of the operating
current of the laser diode 60. Using the operating current control
signal, the control LSI 100 controls the laser control circuit 131
so that the operating current of that value is supplied to the
laser diode 60. The control table contains, for example, data that
indicates the oscillation threshold and the temperature dependence
of the light output versus operating current characteristic of the
laser diode 60. The control table may further contain data that
indicates the relationship between the operating current value and
a temperature increase of the magnetic recording layer heated by
the near-field light 47, and data that indicates the temperature
dependence of the coercivity of the magnetic recording layer.
[0153] As shown in FIG. 13, the control circuit 230 has the signal
system for controlling the laser diode 60, i.e., the signal system
consisting of the laser ON/OFF signal and the operating current
control signal, independent of the control signal system intended
for read/write operations. This configuration makes it possible to
implement various modes of energization of the laser diode 60, not
only to energize the laser diode 60 simply in association with a
write operation. It should be noted that the circuit configuration
of the control circuit 230 is not limited to the one shown in FIG.
13.
[0154] Now, a description will be given of a method of
manufacturing the thermally-assisted magnetic recording head 1
according to the present embodiment. The method of manufacturing
the thermally-assisted magnetic recording head 1 includes the step
of manufacturing the slider 10 and the step of fixing the light
source unit 50 to the slider 10. Here, the method of manufacturing
the slider 10 will be described briefly. The method of
manufacturing the slider 10 includes the steps of: forming
components of a plurality of sliders 10 other than the slider
substrates 11 on a substrate that includes portions to become the
slider substrates 11 of the plurality of sliders 10, thereby
fabricating a substructure that includes a plurality of rows of
pre-slider portions, the pre-slider portions being intended to
become the sliders 10 later; and forming the plurality of sliders
10 by cutting the substructure to separate the plurality of
pre-slider portions from each other. In the step of forming the
plurality of sliders 10, the surfaces formed by the cutting are
polished into the medium facing surfaces 11a and 12a.
[0155] The method of manufacturing the thermally-assisted magnetic
recording head 1 (the method of manufacturing the slider 10)
according to the present embodiment includes the steps of: forming
the waveguide; forming the plasmon generator 34 after the formation
of the wave guide; and forming the magnetic pole 35 after the
formation of the plasmon generator 34. The step of forming the
waveguide includes the steps of forming the clad layer 31; forming
the core 32 on the clad layer 31; and forming the clad layer 33 to
cover the clad layer 31 and the core 32.
[0156] The step of forming the clad layer 33, the step of forming
the plasmon generator 34, and the step of forming the magnetic pole
35 will now be described in detail with reference to FIG. 14 to
FIG. 21. FIG. 14 to FIG. 21 are cross-sectional views each showing
a part of a stack of layers fabricated in the process of
manufacturing the thermally-assisted magnetic recording head 1.
FIG. 14 to FIG. 21 each show a cross section in the position where
the medium facing surface 12a is to be formed.
[0157] FIG. 14 shows a step of the method of manufacturing the
thermally-assisted magnetic recording head 1. In this step, the
core 32 of the waveguide is initially formed on the clad layer 31
and then a dielectric layer 33P is formed to cover the clad layer
31 and the core 32. The dielectric layer 33P is to undergo the
formation of the groove 33b therein later to thereby become the
clad layer 33. Next, an etching mask 71 made of, for example,
metal, is formed on the dielectric layer 33P. The etching mask 71
has an opening 71a that has a shape corresponding to the planar
shape of the plasmon generator 34 to be formed later.
[0158] FIG. 15 shows the next step. In this step, the dielectric
layer 33P is initially etched by, for example, reactive ion etching
or ion milling, by using the etching mask 71. The groove 33b is
thereby formed in the dielectric layer 33P. The groove 33b is
formed so that its bottom surface faces the evanescent light
generating surface 32c with a predetermined distance therebetween.
As has been described with reference to FIG. 4, the groove 33b
includes the V-shaped groove portion. The V-shaped groove portion
has the first and second sidewalls 33b1 and 33b2. The etching depth
(dimension in the Z direction) of the groove 33b in the position
where the medium facing surface 12a is to be formed is 110 nm, for
example. With the groove 33b formed therein, the dielectric layer
33P becomes the clad layer 33. Next, the etching mask 71 is
removed. FIG. 16 shows the stack after the removal of the etching
mask 71.
[0159] In FIG. 15, the angle that the first sidewall 33b1 forms
with respect to the direction perpendicular to the top surface 33a
of the clad layer 33 is represented by the symbol .theta..sub.31,
and the angle that the second sidewall 33b2 forms with respect to
the direction perpendicular to the top surface 33a of the clad
layer 33 is represented by the symbol .theta..sub.32. The angle
.theta..sub.31 and the angle .theta..sub.32 are equal. The angles
.theta..sub.31 and .theta..sub.32 fall within the range of 15 to 60
degrees, for example.
[0160] FIG. 17 shows the next step. In this step, the dielectric
film 72 is formed in the groove 33b by ion beam sputtering, for
example. The dielectric film 72 is formed at least on the first and
second sidewalls 33b1 and 33b2 of the V-shaped groove portion of
the groove 33b. The dielectric film 72 includes the first film
portion 72a adhering to the first sidewall 33b1, and the second
film portion 72b adhering to the second sidewall 33b2. FIG. 18
shows the stack after the formation of the dielectric film 72. In
FIG. 18, the border between the upper part 72a1 and the lower part
72a2 and the border between the upper part 72b1 and the lower part
72b2 are shown by respective dotted lines. The groove 33b and the
dielectric film 72 constitute the accommodating part 70 for
accommodating the plasmon generator 34.
[0161] This step is performed under such a condition that in the
first film portion 72a, the lower part 72a2 has a thickness smaller
than that of the upper part 72a1 in the direction perpendicular to
the first sidewall 33b1 and in the second film portion 72b, the
lower part 72b2 has a thickness smaller than that of the upper part
72b1 in the direction perpendicular to the second sidewall 33b2, as
shown in FIG. 18.
[0162] For example, when forming the dielectric film 72 by ion beam
sputtering, the first film portion 72a and the second film portion
72b are alternately formed by changing the angle that the traveling
direction of the center of the material particle flow for forming
the dielectric film 72 forms with respect to the direction
perpendicular to the top surface 33a of the clad layer 33. In FIG.
17, the arrows show the traveling direction of the center of the
material particle flow. When forming the first film portion 72a,
the traveling direction of the center of the material particle flow
for forming the first film portion 72a is set to form an angle
.theta..sub.41 with respect to the direction perpendicular to the
top surface 33a of the clad layer 33, the angle .theta..sub.41
being greater than the angle .theta..sub.32 (see FIG. 15) that the
second sidewall 33b2 forms with respect to the direction
perpendicular to the top surface 33a of the clad layer 33. When
forming the second film portion 72b, the traveling direction of the
center of the material particle flow for forming the second film
portion 72b is set to form an angle .theta..sub.42 with respect to
the direction perpendicular to the top surface 33a of the clad
layer 33, the angle .theta..sub.42 being greater than the angle
.theta..sub.31 (see FIG. 15) that the first sidewall 33b1 forms
with respect to the direction perpendicular to the top surface 33a
of the clad layer 33. For example, when the angles .theta..sub.31
and .theta..sub.32 are 28 degrees and the etching depth of the
groove 33b in the position where the medium facing surface 12a is
to be formed is 110 nm, the angles .theta..sub.41 and
.theta..sub.42 are set to 45 degrees. With the angles
.theta..sub.41 and .theta..sub.42 greater than the angles
.theta..sub.31 and .theta..sub.32, a smaller amount of material
adheres to the first and second sidewalls 33b1 and 33b2 in the
vicinity of the bottom of the groove 33b. As a result, the first
film portion 72a and the second film portion 72b are formed into
the above-mentioned shape.
[0163] The dielectric film 72 can also be formed by ordinary
sputtering with low directivity. Even in such a case, the
dielectric film 72 can be formed so that a smaller amount of
material adheres to the first and second sidewalls 33b1 and 33b2 in
the vicinity of the bottom of the groove 33b.
[0164] FIG. 19 shows the next step. In this step, a metal film 34P
is formed by, for example, sputtering, so as to cover the entire
top surface of the stack shown in FIG. 18. The metal film 34P is to
become the plasmon generator 34 later.
[0165] FIG. 20 shows the next step. In this step, a magnetic layer
351P is formed on the metal film 34P by plating, for example. The
magnetic layer 351P is to become the first layer 351 of the
magnetic pole 35 later. The magnetic layer 351P is formed into a
thickness sufficient for at least filling the accommodating part
70.
[0166] FIG. 21 shows the next step. In this step, the magnetic
layer 351P and the metal film 34P are polished by, for example,
chemical mechanical polishing, until the clad layer 33 is exposed.
As a result, the remaining metal film 34P becomes the plasmon
generator 34, and the remaining magnetic layer 351P becomes the
first layer 351 of the magnetic pole 35. Next, although not shown,
the second layer 352 is formed on the first layer 351 by plating,
for example. This completes the magnetic pole 35.
[0167] When the foregoing substructure is completed, the
substructure is cut near the positions where the medium facing
surfaces 12a are to be formed, so that the plurality of pre-slider
portions are separated from each other. Subsequently, the surfaces
formed by the cutting are polished into the respective medium
facing surfaces 12a.
[0168] The effects of the thermally-assisted magnetic recording
head 1 according to the present embodiment will now be described.
The plasmon generator 34 of the present embodiment has the outer
surface including the plasmon exciting part 341, and has the
near-field light generating part 34g located in the medium facing
surface 12a. The plasmon exciting part 341 faces the evanescent
light generating surface 32c of the core 32 with a predetermined
distance therebetween. Surface plasmons are excited on the plasmon
exciting part 341 through coupling with the evanescent light that
occurs from the evanescent light generating surface 32c. The
near-field light generating part 34g generates near-field light
based on the surface plasmons excited on the plasmon exciting part
341.
[0169] According to the present embodiment, it is possible to
transform the laser light that is propagated through the core 32
into near-field light with higher efficiency, as compared with the
conventional technique of irradiating a plasmon antenna directly
with laser light to produce near-field light from the plasmon
antenna.
[0170] In the present embodiment, the plasmon exciting part 341
includes the flat surface part 341b. The flat surface part 341b
includes the width changing portion 341b1. The width of the width
changing portion 341b1 in the direction parallel to the medium
facing surface 12a and the evanescent light generating surface 32c
(Y direction) decreases with decreasing distance to the medium
facing surface 12a. In the width changing portion 341b1, as has
been described with reference to FIG. 6, the propagating plasmons
increase in electric field intensity. According to the present
embodiment, it is therefore possible to efficiently enhance the
intensity of the near-field light occurring from the plasmon
generator 34.
[0171] From the foregoing, according to the present embodiment, it
is possible to efficiently use the laser light that is propagated
through the core 32, and to produce intense near-field light from
the plasmon generator 34. The present embodiment also makes it
possible to prevent a part of the medium facing surface 12a from
protruding due to transformation of the energy of the laser light
into thermal energy in the thermally-assisted magnetic recording
head.
[0172] In the present embodiment, the outer surface of the plasmon
generator 34 includes the first inclined surface 342, the second
inclined surface 343, and the front end face 344, in addition to
the plasmon exciting part 341. The first inclined surface 342 and
the second inclined surface 343 are connected to the plasmon
exciting part 341, and increase in distance from each other with
increasing distance from the plasmon exciting part 341. The front
end face 344 is located in the medium facing surface 12a and
connected to the first and second inclined surfaces 342 and 343.
The first inclined surface 342 includes the inclined surface 342a
that is included in the V-shaped portion 34A. The second inclined
surface 343 includes the inclined surface 343a that is included in
the V-shaped portion 34A. The inclined surface 342a includes the
upper part 342a1 and the lower part 342a2 that are continuous with
each other. The inclined surface 343a includes the upper part 343a1
and the lower part 343a2 that are continuous with each other.
[0173] The front end face 344 has the first and second portions
344a and 344b that are connected to each other into a V-shape, and
the bottom end 344c that is closer to the evanescent light
generating surface 32c. The bottom end 344c forms the near-field
light generating part 34g. The first portion 344a includes the
first side 345a lying at the end of the first inclined surface 342
(inclined surface 342a). The second portion 344b includes the
second side 345b lying at the end of the second inclined surface
343 (inclined surface 343a). The first side 345a includes the upper
part 345a1 and the lower part 345a2 that are continuous with each
other. The second side 345b includes the upper part 345b1 and the
lower part 345b2 that are continuous with each other.
[0174] The upper parts 342a1 and 343a1 of the inclined surfaces
342a and 343a and the upper parts 345a1 and 345b1 of the sides 345a
and 345b each have an inclination angle of .theta..sub.1. The lower
parts 342a2 and 343a2 of the inclined surfaces 342a and 343a and
the lower parts 345a2 and 345b2 of the sides 345a and 345b each
have an inclination angle of .theta..sub.2. The angle
2.theta..sub.2 formed between the lower part 345a2 and the lower
part 345b2 is smaller than the angle 2.theta..sub.1 formed between
the upper part 345a1 and the upper part 345b1.
[0175] According to the present embodiment, between the two types
of angles .theta..sub.1 and .theta..sub.2, the angle .theta..sub.1
in particular is set to an appropriate value. This makes it
possible to match the wave number of the surface plasmons to be
excited on the plasmon generator 34 with the wave number of the
evanescent light which depends on the wavelength of the laser light
to be propagated through the core 32. It is thereby possible to
increase the intensity of the surface plasmons to be excited on the
plasmon generator 34. According to the present embodiment, reducing
the angle 2.theta..sub.2 between the lower part 345a2 of the first
side 345a and the lower part 345b2 of the second side 345b allows
forming the front end face 344 of the plasmon generator 34 into a
more sharply pointed shape in the vicinity of the bottom end 344c
which constitutes the near-field light generating part 34g. This
makes it possible to reduce the spot diameter of the near-field
light. According to the present embodiment, it is thus possible to
reduce the spot diameter of the near-field light while matching the
wave number of the evanescent light with the wave number of the
surface plasmons to be excited on the plasmon generator 34.
Consequently, according to the present embodiment, it is possible
to use the light propagated through the core 32 of the waveguide
with high efficiency and to produce near-field light with a small
spot diameter from the plasmon generator 34.
[0176] In the present embodiment, the groove 33b of the clad layer
33 and the dielectric film 72 constitute the accommodating part 70
for accommodating the plasmon generator 34. The groove 33b includes
the V-shaped groove portion. The V-shaped groove portion includes
the first and second sidewalls 33b1 and 33b2 that increase in
distance from each other with increasing distance from the top
surface 33a of the clad layer 33. The dielectric film 72 includes
the first film portion 72a adhering to the first sidewall 33b1, and
the second film portion 72b adhering to the second sidewall 33b2.
The first film portion 72a includes the upper part 72a1 and the
lower part 72a2 that are continuous with each other. The second
film portion 72b includes the upper part 72b1 and the lower part
72b2 that are continuous with each other. In the first film portion
72a, the lower part 72a2 has a thickness smaller than that of the
upper part 72a1 in the direction perpendicular to the first
sidewall 33b1. In the second film portion 72b, the lower part 72b2
has a thickness smaller than that of the upper part 72b1 in the
direction perpendicular to the second sidewall 33b2.
[0177] Forming the plasmon generator 34 to be accommodated in such
an accommodating part 70 makes it easy to provide the plasmon
generator 34 with the shape described above.
[0178] A description will now be given of the results of a
simulation demonstrating that the plasmon generator 34 having the
above-described shape allows the efficient use of the laser light
propagated through the core 32 and allows generation of near-field
light with a small spot diameter from the plasmon generator 34.
Initially, a plurality of models of the thermally-assisted magnetic
recording head that were used in the simulation will be described.
The plurality of models that were used in the simulation include a
plurality of models of first type in which the lower parts 345a2
and 345b2 of the sides 345a and 345b have an inclination angle
.theta..sub.2 of 10 degrees, a plurality of models of second type
with .theta..sub.2 of 15 degrees, and a plurality of models of
third type with .theta..sub.2 of 20 degrees.
[0179] In all the models, tantalum oxide was selected as the
material of the core 32, Au was selected as the material of the
plasmon generator 34, alumina was selected as the material of the
clad layers 31 and 33 and the dielectric film 72, and FeCo alloy
was selected as the material of the magnetic pole 35. The width
W.sub.WG of the evanescent light generating surface 32c of the core
32 in the vicinity of the plasmon generator 34 and the thickness
T.sub.WG of the core 32 were both set to 0.4 .mu.m. Each of the two
sides 32b3 and 32b4 of the end face 32b of the core 32 was set to
form an angle .theta..sub.WG of 5 degrees with respect to the
direction perpendicular to the top side 32b1.
[0180] In all the models, the distance T.sub.BF between the plasmon
exciting part 341 and the evanescent light generating surface 32c
was set to 50 nm. The distance D between the bottom end 344c of the
front end face 344 of the plasmon generator 34 and the tip 35c of
the end face 35a1 of the first layer 351 of the magnetic pole 35
was set to 35 nm. The dimension T.sub.PG of the plasmon generator
34 in the Z direction at the medium facing surface 12a was set to
110 nm. The dimension W.sub.PGL of the third portion 34C of the
plasmon generator 34 in the track width direction TW (Y direction)
was set to 400 nm. The length H.sub.PG of the plasmon generator 34
in the X direction was set to 1.5 .mu.m. The length H.sub.PGA of
the V-shaped portion 34A of the plasmon generator 34 in the X
direction was set to 0.1 .mu.m.
[0181] In all the models, the inclination angle .theta..sub.1 of
each of the upper parts 345a1 and 345b1 of the sides 345a and 345b
was set to 28 degrees. Each of the inclined surfaces 342c and 343c
of the third portion 34C was set to form an angle of 33 degrees
with respect to the direction perpendicular to the evanescent light
generating surface 32c.
[0182] The distance T.sub.PG2 shown in FIG. 5 was set to different
values between the first to third types within the range of 0 nm to
40 nm. It should be noted that T.sub.PG2=0 nm means the absence of
the lower parts 342a2 and 343a3 of the inclined surfaces 342a and
343a and the lower parts 345a2 and 345b2 of the sides 345a and
345b.
[0183] In the simulation, a Gaussian beam with a wavelength of 800
nm was selected as the laser light to be propagated through the
core 32. The light density distribution of the near-field light at
the surface of a magnetic recording medium 201 located 6 nm away
from the medium facing surface 12a was then determined by using a
three-dimensional finite-difference time-domain method (FDTD
method). From the light density distribution, the spot diameter of
the near-field light (hereinafter, referred to as a light spot
diameter) and the maximum light density were determined. The light
spot diameter was defined as the full width at half maximum in the
light density distribution.
[0184] Table 1 and FIG. 22 show the result of the simulation using
the plurality of models of first type. Table 2 and FIG. 23 show the
result of the simulation using the plurality of models of second
type. Table 3 and FIG. 24 show the result of the simulation using
the plurality of models of third type. In FIG. 22 to FIG. 24, the
horizontal axis indicates the distance T.sub.PG2 shown in FIG. 5,
the vertical axis on the left indicates the light spot diameter,
and the vertical axis on the right indicates the maximum light
density.
TABLE-US-00001 TABLE 1 T.sub.PG2 (nm) Maximum light density
(V.sup.2/m.sup.2) Light spot diameter (nm) 0 1.38 118 5 1.43 106 10
1.45 96 15 1.47 87 20 1.47 81 25 1.46 81 30 1.42 79 35 1.36 79 40
1.30 78
TABLE-US-00002 TABLE 2 T.sub.PG2 (nm) Maximum light density
(V.sup.2/m.sup.2) Light spot diameter (nm) 0 1.38 118 5 1.48 110 10
1.53 103 15 1.56 97 20 1.57 93 25 1.53 93 30 1.44 92 35 1.38 92 40
1.33 91
TABLE-US-00003 TABLE 3 T.sub.PG2 (nm) Maximum light density
(V.sup.2/m.sup.2) Light spot diameter (nm) 0 1.38 118 5 1.55 111 10
1.63 105 15 1.68 104 20 1.70 103 25 1.63 103 30 1.44 102 35 1.33
102 40 1.20 102
[0185] From Table 1 to Table 3 and FIG. 22 to FIG. 24, it can be
seen that the light spot diameter decreases with increasing
T.sub.PG2. It is also shown that the maximum light density peaks at
around T.sub.PG2=20 nm, and falls off away from T.sub.PG2=20 nm. It
is preferred that the light spot diameter be as small as possible,
and that the maximum light density be as high as possible. Based on
the results shown in Table 1 to Table 3 and FIG. 22 to FIG. 24, the
range of 105 nm and smaller is selected as the preferred range of
the light spot diameter so as to exclude relatively large light
spot diameters. The range of 1.45 V.sup.2/m.sup.2 and higher is
selected as the preferred range of the maximum light density so as
to exclude relatively low maximum light densities. The light spot
diameter and the maximum light density fall within the respective
preferred ranges if T.sub.PG2 is in the range of 10 nm to 25 nm.
That is, when T.sub.PG2 is in the range of 10 nm to 25 nm, the
light spot diameter can be made relatively smaller and the maximum
light density relatively higher as compared with the case where
T.sub.PG2 is out of the range. Consequently, T.sub.PG2 preferably
falls within the range of 10 nm to 25 nm. When T.sub.PG2 is in the
range of 10 nm to 25 nm, the light spot diameter is smaller and the
maximum light density is higher than when T.sub.PG2=0 nm. It can
thus be seen that the present embodiment makes it possible to
reduce the light spot diameter and increase the maximum light
density as well.
[0186] As can be seen from the results of the simulation described
above, it is possible according to the present embodiment to
efficiently use the laser light that is propagated through the core
32 and to produce near-field light with a small spot diameter from
the plasmon generator 34.
[0187] The other effects of the present embodiment will now be
described. Initially, a description will be given of the effect
resulting from the configuration that the flat surface part 341b of
the plasmon exciting part 341 of the plasmon generator 34 includes
the constant width portion 341b2. Suppose that the flat surface
part 341b does not include the constant width portion 341b2, and
the width changing portion 341b1 extends up to the end of the flat
surface part 341b opposite from the medium facing surface 12a. In
such a case, the maximum width of the flat surface part 341b is
greater as compared with the case where the flat surface part 341b
includes the constant width portion 341b2. Then, the width W.sub.WG
of the evanescent light generating surface 32c of the core 32 in
the vicinity of the plasmon generator 34 needs to be increased to
the maximum width of the flat surface part 341b. Consequently, at
least a part of the core 32 in the vicinity of the plasmon
generator 34 is likely to enter a multi mode that is capable of
propagating a plurality of modes (propagation modes) of light. In
this case, the mode that contributes to the excitation of surface
plasmons on the flat surface part 341b weakens to decrease the use
efficiency of the light that is propagated through the core 32. In
contrast, according to the present embodiment, the flat surface
part 341b includes the constant width portion 341b2, and it is
therefore possible to make the width W.sub.WG of the evanescent
light generating surface 32c of the core 32 in the vicinity of the
plasmon generator 34 smaller than that in the case where the flat
surface part 341b does not include the constant width portion
341b2. According to the present embodiment, it is therefore
possible to bring at least a part of the core 32 in the vicinity of
the plasmon generator 34 into a single mode that is capable of
propagating only a single mode of light. Consequently, it is
possible to improve the use efficiency of the laser light that is
propagated through the core 32.
[0188] Next, a description will be given of the effect resulting
from the configuration that the plasmon generator 34 has the
V-shaped portion 34A and the propagative edge 341a. As described
previously, the medium facing surface 12a is formed by polishing a
surface that is formed by cutting the substructure. In such a case,
the position of the medium facing surface 12a may slightly vary.
Suppose that the plasmon generator 34 is designed not to have the
V-shaped portion 34A or the propagative edge 341a so that the ends
of the second portion 34B and the width changing portion 341b1 are
located in the medium facing surface 12a. If so, variations in the
position of the medium facing surface 12a change the shape of the
front end face 344 of the plasmon generator 34, or the shape of the
bottom end 344c in particular. As a result, the near-field light
occurring from the plasmon generator 34 can vary in characteristic.
In contrast, according to the present embodiment, the plasmon
generator 34 has the V-shaped portion 34A and the propagative edge
341a. This makes it possible that, even if the position of the
medium facing surface 12a somewhat varies, the front end face 344
of the plasmon generator 34 remains unchanged in shape. According
to the present embodiment, it is therefore possible to prevent the
characteristics of the near-field light generated by the plasmon
generator 34 from being changed due to variations in the position
of the medium facing surface 12a.
[0189] Next, a description will be given of the effect resulting
from the configuration that the magnetic pole 35 is disposed such
that the plasmon generator 34 is interposed between the magnetic
pole 35 and the core 32. With such a configuration, according to
the present embodiment, the end face of the magnetic pole 35 for
generating the write magnetic field (the end face 35a1 of the first
layer 351) and the near-field light generating part 34g of the
plasmon generator 34 for generating the near-field light can be put
close to each other in the medium facing surface 12a. This makes it
possible to implement an advantageous configuration for
thermally-assisted magnetic recording. Moreover, according to the
present embodiment, since the plasmon generator 34 made of a
nonmagnetic metal is interposed between the core 32 and the
magnetic pole 35, it is possible to prevent the laser light
propagated through the core 32 from being absorbed by the magnetic
pole 35. This can improve the use efficiency of the laser light
propagated through the core 32.
[0190] In the present embodiment, the magnetic pole 35 is in
contact with the plasmon generator 34. The magnetic pole 35 is also
in contact with the top yoke layer 43 of high volume via the
coupling layer 36. Consequently, according to the present
embodiment, the heat occurring from the plasmon generator 34 can be
dissipated through the magnetic pole 35, the coupling layer 36, and
the top yoke layer 43. This can suppress an excessive rise in
temperature of the plasmon generator 34, so that the front end face
344 of the plasmon generator 34 will not protrude from the medium
facing surface 12a, nor will the plasmon generator 34 drop in use
efficiency of the light. Moreover, according to the present
embodiment, the plasmon generator 34 made of a metal is in contact
with the magnetic pole 35 made of a magnetic metal material. The
plasmon generator 34 is thus not electrically isolated. According
to the present embodiment, it is therefore possible to avoid the
occurrence of electrical static discharge (ESD) in the plasmon
generator 34.
[0191] In the present embodiment, the front end face 344 of the
plasmon generator 34 has the two portions 344a and 344b that are
connected to each other into a V-shape. The end face 35a of the
magnetic pole 35 located in the medium facing surface 12a includes
a generally triangular portion interposed between the two portions
344a and 344b of the front end face 344, that is, the end face 35a1
of the first layer 351. The end face 35a1 has the tip 35c located
at its bottom end. In the end face 35a of the magnetic pole 35, the
tip 35c is closest to the bottom shield layer 29. Magnetic fluxes
therefore concentrate at the vicinity of the tip 35c of the end
face 35a of the magnetic pole 35, so that a high write magnetic
field occurs from the vicinity of the tip 35c. Consequently,
according to the present embodiment, the position where a high
write magnetic field occurs in the end face 35a of the magnetic
pole 35 can be brought closer to the near-field light generating
part 34g of the plasmon generator 34 which generates near-field
light. According to the present embodiment, it is thus possible to
put the position of occurrence of the write magnetic field and the
position of occurrence of the near-field light close to each other
while preventing the laser light propagated through the core 32
from being absorbed by the magnetic pole 35.
[0192] The plasmon generator 34 has the V-shaped portion 34A which
is V-shaped in cross section parallel to the medium facing surface
12a. The magnetic pole 35 includes a generally
triangular-prism-shaped portion accommodated in the V-shaped
portion 34A, that is, the first portion 351A of the first layer
351. The width of the first portion 351A in the direction parallel
to the medium facing surface 12a and the evanescent light
generating surface 32c (Y direction) does not change according to
the distance from the medium facing surface 12a. According to the
present embodiment, it is therefore possible to keep the shape of
the end face 35a1 of the first layer 351 constant even if the
position of the medium facing surface 12a somewhat varies.
Consequently, according to the present embodiment, it is possible
to suppress a change in the write characteristics due to variations
in the position of the medium facing surface 12a.
[0193] The plasmon generator 34 further has the second portion 34B.
The second portion 34B has the bottom part 34B1 and the two
sidewall parts 34B2 and 34B3. The width of the bottom part 34B1 in
the direction parallel to the medium facing surface 12a and the
evanescent light generating surface 32c (Y direction) decreases
with decreasing distance to the medium facing surface 12a. The
distance between the two sidewall parts 34B2 and 34B3 in the
direction parallel to the medium facing surface 12a and the
evanescent light generating surface 32c (Y direction) increases
with increasing distance from the evanescent light generating
surface 32c, and decreases with decreasing distance to the medium
facing surface 12a. The magnetic pole 35 includes the second
portion 351B that is interposed between the two sidewall parts 34B2
and 34B3 and in contact with the bottom part 34B1 and the two
sidewall parts 34B2 and 34B3. The width of the second portion 351B
in the direction parallel to the medium facing surface 12a and the
evanescent light generating surface 32c (Y direction) decreases
with decreasing distance to the medium facing surface 12a.
Consequently, according to the present embodiment, magnetic fluxes
passing through the magnetic pole 35 can be concentrated as they
approach the first portion 351A of the first layer 351 of the
magnetic pole 35. This makes it possible to produce a high write
magnetic field from the end face 35a1.
Second Embodiment
[0194] A second embodiment of the invention will now be described
with reference to FIG. 25. FIG. 25 is a front view showing a part
of the medium facing surface of the head unit of the
thermally-assisted magnetic recording head according to the present
embodiment. The thermally-assisted magnetic recording head
according to the present embodiment has a plasmon generator 84
instead of the plasmon generator 34 of the first embodiment.
Although not shown, the plasmon generator 84 has a V-shaped
portion, a second portion, and a third portion, as does the plasmon
generator 34 of the first embodiment. The outer surface of the
plasmon generator 84 includes the front end face 344, as does the
plasmon generator 34 of the first embodiment.
[0195] The thermally-assisted magnetic recording head according to
the present embodiment has a magnetic pole 85 instead of the
magnetic pole 35 of the first embodiment. The magnetic pole 85
includes a first layer 851, and a second layer 852 on the first
layer 851. The V-shaped portion, the second portion, and the third
portion of the plasmon generator 84 form inside a space for
accommodating the first layer 851 of the magnetic pole 85. Although
not shown, the first layer 851 includes a first portion, a second
portion, and a third portion, as does the first layer 351 of the
first embodiment. The second layer 852 is greater than the first
layer 851 in width in the direction parallel to the medium facing
surface 12a and the evanescent light generating surface 32c (Y
direction).
[0196] The magnetic pole 85 has an end face 85a located in the
medium facing surface 12a. The end face 85a includes an end face
85a1 of the first layer 851 located in the medium facing surface
12a and an end face 85a2 of the second layer 852 located in the
medium facing surface 12a. The end face 85a1 is generally
triangle-shaped and is interposed between the two portions 344a and
344b of the front end face 344 of the plasmon generator 84.
[0197] The plasmon generator 84 further has two extended portions
84A and 84B that spread out from the top ends of the V-shaped
portion, the second portion and the third portion of the plasmon
generator 84 in the direction parallel to the medium facing surface
12a and the evanescent light generating surface 32c (Y direction).
As seen from above, the outer edges of the extended portions 84A
and 84B coincide with or lie close to the outer edges of the second
layer 852 of the magnetic pole 85. The bottom surfaces of the
extended portions 84A and 84B are in contact with the top surface
33a of the clad layer 33. The top surfaces of the extended portions
84A and 84B are in contact with the bottom surface of the second
layer 852.
[0198] The remainder of configuration, function and effects of the
present embodiment are similar to those of the first
embodiment.
Third Embodiment
[0199] A third embodiment of the invention will now be described
with reference to FIG. 26. FIG. 26 is a perspective view showing
the core of the waveguide, the plasmon generator, and the magnetic
pole of the thermally-assisted magnetic recording head according to
the present embodiment. The thermally-assisted magnetic recording
head according to the present embodiment has a plasmon generator 94
instead of the plasmon generator 34 of the first embodiment. The
plasmon generator 94 has a V-shaped portion 94A having an end face
located in the medium facing surface 12a. The V-shaped portion 94A
extends in the direction perpendicular to the medium facing surface
12a (X direction). In the present embodiment, in particular, the
entire plasmon generator 94 is composed of the V-shaped portion
94A. In the cross section parallel to the medium facing surface
12a, the V-shaped portion 94A has the same shape as that of the
V-shaped portion 34A of the plasmon generator 34 of the first
embodiment.
[0200] The plasmon generator 94 has a near-field light generating
part 94g located in the medium facing surface 12a. The outer
surface of the plasmon generator 94 includes a propagative edge
941, a first inclined surface 942, a second inclined surface 943,
and a front end face 944. The propagative edge 941 functions as a
plasmon exciting part that faces the evanescent light generating
surface 32c with a predetermined distance therebetween. The
propagative edge 941 connects respective ends of the inclined
surfaces 942 and 943 to each other, the ends being closer to the
evanescent light generating surface 32c. The near-field light
generating part 94g lies at an end of the propagative edge 941. The
first and second inclined surfaces 942 and 943 increase in distance
from each other with increasing distance from the propagative edge
941.
[0201] The front end face 944 has two portions 944a and 944b that
are connected to each other into a V-shape. The front end face 944
further has a bottom end 944c that is closer to the evanescent
light generating surface 32c. The bottom end 944c forms the
near-field light generating part 94g. The front end face 944 has
the same shape as that of the front end face 344 of the plasmon
generator 34 of the first embodiment.
[0202] The magnetic pole 35 of the present embodiment includes a
first layer 351, and a second layer 352 on the first layer 351. The
first layer 351 is generally triangular-prism-shaped. The first
layer 351 is accommodated in the V-shaped portion 94A and is in
contact with the V-shaped portion 94A. The magnetic pole 35 has an
end face 35a located in the medium facing surface 12a. The end face
35a includes an end face 35a1 of the first layer 351 located in the
medium facing surface 12a and an end face 35a2 of the second layer
352 located in the medium facing surface 12a. The end face 35a1 is
generally triangle-shaped and is interposed between the two
portions 944a and 944b of the front end face 944 of the plasmon
generator 94. The end face 35a1 has a tip 35c located at its bottom
end. The second layer 352 has a bottom surface that is in contact
with the top surface of the first layer 351 and the top end surface
of the V-shaped portion 94A of the plasmon generator 94.
[0203] The remainder of configurations of the thermally-assisted
magnetic recording head, the head gimbal assembly, and the magnetic
recording device according to the present embodiment are the same
as in the first embodiment. The function and effects of the
thermally-assisted magnetic recording head according to the present
embodiment are the same as in the first embodiment except the
function and effects resulting from the second portion 34B and the
third portion 34C of the plasmon generator 34 of the first
embodiment the second portion 351B and the third portion 351C of
the first layer 351 of the magnetic pole 35 of the first
embodiment.
[0204] The present invention is not limited to the foregoing
embodiments, and various modifications may be made thereto. For
example, the plasmon generator of the present invention may be
configured such that the V-shaped portion 34A is omitted from the
plasmon generator 34 of the first embodiment. In such a case, an
end of the second portion 34B is located in the medium facing
surface 12a. The first layer 351 of the magnetic pole 35 in this
case does not have the first portion 351A, so that an end of the
second portion 351B is located in the medium facing surface 12a.
Even in such a case, according to the invention, the front end face
of the plasmon generator shall have the same shape as that of the
front end face 344 of the plasmon generator 34 of the first
embodiment.
[0205] It is apparent that the present invention can be carried out
in various forms and modifications in the light of the foregoing
descriptions. Accordingly, within the scope of the following claims
and equivalents thereof, the present invention can be carried out
in forms other than the foregoing most preferable embodiments.
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