U.S. patent application number 14/250522 was filed with the patent office on 2015-10-15 for thermal assisted magnetic recording head utilizing uncoupled light.
This patent application is currently assigned to TDK Corporation. The applicant listed for this patent is TDK Corporation. Invention is credited to Shinji HARA, Eiji KOMURA, Daisuke MIYAUCHI, Norikazu OTA, Tetsuya ROPPONGI, Koji SHIMAZAWA.
Application Number | 20150294678 14/250522 |
Document ID | / |
Family ID | 54265593 |
Filed Date | 2015-10-15 |
United States Patent
Application |
20150294678 |
Kind Code |
A1 |
HARA; Shinji ; et
al. |
October 15, 2015 |
THERMAL ASSISTED MAGNETIC RECORDING HEAD UTILIZING UNCOUPLED
LIGHT
Abstract
A thermal assisted magnetic recording head has a magnetic head
slider having an air bearing surface that is opposite to a magnetic
recording medium, a core that can propagate laser light as
propagating light, a plasmon generator that includes a generator
front end surface facing the air bearing surface, and a main pole
facing the air bearing surface, and a laser light generator that
supplies the laser light to the core. The plasmon generator
generates near-field light (NF light) at the generator front end
surface to heat the magnetic recording medium. The main pole
includes a main pole end surface that faces the air bearing surface
and that is positioned in the vicinity of the generator front end
surface, and emits a magnetic flux to the magnetic recording medium
from the main pole end surface. At least a portion of the laser
light that is not coupled with the plasmon generator thermally
deforms the air bearing surface so that a part of the air bearing
surface positioned closer to the leading side than the generator
front end surface and the main pole end surface in the down track
direction protrudes toward the magnetic recording medium.
Inventors: |
HARA; Shinji; (Tokyo,
JP) ; KOMURA; Eiji; (Tokyo, JP) ; OTA;
Norikazu; (Tokyo, JP) ; MIYAUCHI; Daisuke;
(Tokyo, JP) ; ROPPONGI; Tetsuya; (Tokyo, JP)
; SHIMAZAWA; Koji; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TDK Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
TDK Corporation
Tokyo
JP
|
Family ID: |
54265593 |
Appl. No.: |
14/250522 |
Filed: |
April 11, 2014 |
Current U.S.
Class: |
369/13.33 ;
29/603.07 |
Current CPC
Class: |
G11B 2005/0021 20130101;
G11B 5/6076 20130101; G11B 7/1387 20130101; G11B 13/08 20130101;
G11B 5/6082 20130101; G11B 5/3106 20130101; G11B 5/3163 20130101;
G11B 5/6088 20130101; G11B 5/314 20130101 |
International
Class: |
G11B 5/48 20060101
G11B005/48; G11B 5/60 20060101 G11B005/60; G11B 5/31 20060101
G11B005/31 |
Claims
1. A thermal assisted magnetic recording head, comprising: a
magnetic head slider, comprising: an air bearing surface opposite
to a magnetic recording medium, a core that can propagate laser
light as propagating light, a plasmon generator that includes a
generator front end surface facing the air bearing surface, and a
main pole facing the air bearing surface; and a laser light
generator that supplies the laser light to the core, wherein the
plasmon generator is opposite to a part of the core and extends to
the generator front end surface, is coupled with a portion of the
propagating light that propagates through the core in a surface
plasmon mode and generates surface plasmon, propagates the surface
plasmon to the generator front end surface, and generates
near-field light (NF light) at the generator front end surface to
heat the magnetic recording medium, the main pole includes a main
pole end surface that faces the air bearing surface and that is
positioned in the vicinity of the generator front end surface, and
that emits magnetic flux to the magnetic recording medium from the
main pole end surface, and at least a portion of the laser light
that is not coupled with the plasmon generator thermally deforms
the air bearing surface, so that a part of the air bearing surface,
which is positioned closer to the leading side than the generator
front end surface and the main pole end surface in a down track
direction, protrudes toward the magnetic recording medium.
2. The thermal assisted magnetic recording head according to claim
1, wherein the part of the air bearing surface protrudes more
toward the magnetic recording medium than the generator front end
surface and the main pole end surface.
3. The thermal assisted magnetic recording head according to claim
1, wherein at least the portion of the laser light is the laser
light that is not coupled with the core as the propagating
light.
4. The thermal assisted magnetic recording head according to claim
1, wherein an emission center of the laser light generator is
shifted toward the leading side in the down track direction from a
position with the highest coupling efficiency to the core.
5. The thermal assisted magnetic recording head according to claim
4, wherein a position with the highest coupling efficiency to the
core is on an extension of the central axis of the core.
6. The thermal assisted magnetic recording head according to claim
5, wherein an offset distance between the emission center of the
laser light generator and the central axis of the core in the down
track direction is within the range of 0 to 37.5% (excluding 0%) of
the down track direction-dimension of the core.
7. The thermal assisted magnetic recording head according to claim
1, further comprising: a leading shield that includes a shield end
surface that faces the air bearing surface, that is positioned
closer to the leading side than the generator front end surface,
that is magnetically coupled with the main pole, and that absorbs
magnetic flux returning from the magnetic recording medium, wherein
the part of the air bearing surface is the shield end surface.
8. The thermal assisted magnetic recording head according to claim
1, wherein at least the portion of the laser light is the
propagating light that is coupled with the core, but is not coupled
with the plasmon generator.
9. The thermal assisted magnetic recording head according to claim
8, wherein the core comprises: a first part that includes an
incident end surface of the laser light; a second part that
includes a part opposite to the plasmon generator, and where its
width in the cross track direction is narrower than a width of the
first part in the cross track direction; and a third part that
links the first part and the second part, and where its width in
the cross track direction changes in the direction that is
orthogonal to the air bearing surface.
10. A head gimbal assembly, comprising: the thermal assisted
magnetic recording head according to claim 1, and a suspension that
elastically supports the thermal assisted magnetic recording head,
wherein the suspension comprises: a flexure to which the thermal
assisted magnetic recording head is joined, a load beam having one
end connected to the flexure, and a base plate which is connected
to the other end of the load beam.
11. A magnetic recording device, comprising: the magnetic recording
medium that positions to be opposite to the thermal assisted
magnetic recording head according to claim 1, a spindle motor that
rotates and drives the magnetic recording medium, and a device that
supports the magnetic head slider and that positions the magnetic
head slider with respect to the magnetic recording medium.
12. A manufacturing method for a thermal assisted magnetic
recording head, wherein the thermal assisted magnetic recording
head comprises: a magnetic head slider, comprising: an air bearing
surface opposite to a magnetic recording medium, a core that can
propagate laser light as propagating light, a plasmon generator
that includes a generator front end surface facing the air bearing
surface, and a main pole facing the air bearing surface; and a
laser light generator that supplies the laser light to the core,
wherein the plasmon generator is opposite to a part of the core and
extends to the generator front end surface, is coupled with a
portion of the propagating light that propagates through the core
in a surface plasmon mode and generates surface plasmon, propagates
the surface plasmon to the generator front end surface, and
generates near-field light at the generator front end surface to
heat the magnetic recording medium, the main pole includes a main
pole end surface that faces the air bearing surface and is
positioned in the vicinity of the generator front end surface, and
emits a magnetic flux to the magnetic recording medium from the
main pole end surface; and the manufacturing method including:
targeting a predetermined positional relationship between the laser
light generator and the magnetic head slider; affixing the laser
diode unit including the laser light generator to the magnetic head
slider; and in the positional relationship, coupling a portion of
the laser light with the core, and shifting an emission center of
the laser light generator toward the leading side in the down track
direction from a position with the highest coupling efficiency with
the core.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a thermal assisted magnetic
recording head, and it particularly relates to a thermal assisted
magnetic recording head using a plasmon generator.
[0003] 2. Description of the Related Art
[0004] Recently, in a magnetic recording device typified by a
magnetic disk device, in association with high recording density,
there is a demand for improvement in performance of thin film
magnetic heads and magnetic recording media. As the thin film
magnetic head, composite-type thin film magnetic heads are widely
used in which a reproducing head having a magneto-resistive effect
element (MR element) for reading, and a recording head having an
induction-type electromagnetic transducer element for writing, are
laminated on a substrate.
[0005] The magnetic recording medium is a discontinuous medium
where magnetic grains are aggregated, and each magnetic grain has a
single magnetic domain structure. Each recording bit on the
magnetic recording medium is configured by a plurality of magnetic
grains. In order to increase the recording density, asperities at
the border between adjacent recording bits need to be decreased by
decreasing the size of the magnetic grains. On the other hand,
decreasing the size of the magnetic grains, i.e., decreasing in the
volume of the magnetic grains, results in a decrease in the thermal
stability of magnetization in the magnetic grains. In order to
resolve this problem, it is effective to increase the anisotropic
energy of the magnetic grains. However, the increased anisotropic
energy of the magnetic grains enhances the coercive force of the
magnetic recording medium, making it difficult to record the
information by an existing magnetic head.
[0006] As a method for resolving this problem, so-called thermal
assisted magnetic recording is proposed. In this method, a magnetic
recording medium with a high coercive force can be used. At the
time of recording information, the simultaneous addition of a
magnetic field and heat to a portion of the recording medium where
the information will be recorded increases the temperature of that
portion. This results in information being recorded by the magnetic
field at the portion where the coercive force is decreased.
Hereafter, the magnetic head used for thermal assisted magnetic
recording is referred to as a thermal assisted magnetic recording
head (TAMR head).
[0007] In thermal assisted magnetic recording, a laser light source
is commonly used for heating a magnetic recording medium. As
heating methods, a method to heat a magnetic recording medium with
laser light (direct heating) and a method to convert the laser
light into near-field light (NF light) and heat a magnetic
recording medium (NF light heating) are known.
[0008] As an example of direct heating, in JP 1110-162444, a head
using a solid immersion lens for an optical magnetic disk is
disclosed. The head forms a super fine optical beam spot on an
optical magnetic disk, and records a signal in a super fine
magnetic domain.
[0009] As an example of NF light heating, in JP 2001-255254, an NF
light probe used for optical recording, i.e., a so-called plasmon
antenna is disclosed. The NF light probe is configured with a
metallic scatterer in the shape of a conical body or film-like
triangle formed on a substrate, and a film, such as a dielectric
body formed around the scatterer, and generates NF light from
plasmon excited by light. The NF light is a type of so-called
electromagnetic field formed around the periphery of a material,
and diffraction limitations due to the wavelength of the light can
be ignored. By irradiating a microstructure with light having the
same wavelength, NF light depending upon the scale of the
microstructure is formed, and it is even possible to focus light
onto a very small domain on the order of tens of nm.
[0010] In JP 2004-158067, an NF light probe used for a single
magnetic pole for perpendicular magnetic recording head is
disclosed. The NF light probe is a scatterer made of gold, and is
formed to be perpendicular to the magnetic recording medium
contacting the main pole.
[0011] One of the problems of the TAMR head is the reliability of
the plasmon antenna against heat. As described in JP 2001-255254
and JP 2004-158067, when light is directly irradiated to the
plasmon antenna, the temperature of the plasmon antenna drastically
rises, and the thermal reliability decreases. In US2010/0103553,
instead of directly irradiating the plasmon antenna with light
propagating through the core, a technology is disclosed in which
the surface plasmon is excited at a plasmon generator adjacent to
the core via a buffer layer. The propagating light is coupled with
a plasmon generator in a surface plasmon polariton mode, and
excites the surface plasmon at the plasmon generator. Specifically,
evanescent light which penetrates the buffer layer is generated at
an interface by the total reflection of the light propagating
through the core at the interface of the core and the buffer layer.
Collective vibration of electric charges in the plasmon generator,
i.e., surface plasmon, is coupled with the evanescent light, and
the surface plasmon is excited at the plasmon generator. The
surface plasmon excited at the plasmon generator propagates to the
generator front end surface via a propagation edge, and generates
NF light at the generator front end surface. According to this
technology, because light that propagates through the core is not
directly irradiated to the plasmon generator, it is possible to
prevent an excessive temperature increase at the plasmon generator.
Such a plasmon generator is referred to as a surface evanescent
light coupling type NF light generator.
[0012] However, in current TAMR, deterioration of recording
characteristics (such as the S/N ratio) in association with
continuous recording has been confirmed. As the main factor,
agglomeration of the generator front end surface of the plasmon
generator is recognized. The agglomeration is a phenomenon where
metal atoms gather, and it occurs as a result of diffusion and
movement of the metal atoms using heat and stress as the driving
force. Asperities exist on an air bearing surface of the magnetic
head slider and a surface of the magnetic recording medium, and the
generator front end surface of the plasmon generator may make
contact with the magnetic recording medium during the operation of
the magnetic recording device. The temperature increase and stress
increase due to the impact occurring at this time cause the
agglomeration. In general, because metal formed by sputtering or a
plating method has low density, the density is gradually increased
due to heat or stress, and the volume is easily reduced. Since the
plasmon generator is normally formed by sputtering, agglomeration
and a recess from the air bearing surface in association with the
agglomeration easily occur. As a result, the distance between the
plasmon generator and the magnetic recording medium is increased,
and the capability to heat the magnetic recording medium decreases
over time, causing the deterioration of the S/N ratio. Therefore,
it is desirable to suppress the agglomeration of the plasmon
generator in order to secure the reliability of the TAMR head.
[0013] The object of the present invention is to provide a TAMR
head with high reliability where the agglomeration of the generator
front end surface of the plasmon generator rarely occurs, and the
manufacturing method thereof.
SUMMARY OF THE INVENTION
[0014] The thermal assisted magnetic recording head of the present
invention has a magnetic head slider having an air bearing surface
that is opposite to a magnetic recording medium, a core that can
propagate laser light as propagating light, a plasmon generator
that includes a generator front end surface facing the air bearing
surface, and a main pole facing the air bearing surface, and a
laser light generator that supplies the laser light to the core.
The plasmon generator is opposite to a part of the core and extends
to the generator front end surface, is coupled with a portion of
the propagating light that propagates through the core in the
surface plasmon mode and generates surface plasmon, propagates the
surface plasmon to the generator front end surface, and generates
near-field light (NF light) at the generator front end surface to
heat the magnetic recording medium. The main pole includes a main
pole end surface that faces the air bearing surface and that is
positioned in the vicinity of the generator front end surface, and
emits a magnetic flux to the magnetic recording medium from the
main pole end surface. At least a portion of the laser light that
is not coupled with the plasmon generator thermally deforms the air
bearing surface so that a part of the air bearing surface
positioned closer to the leading side than the generator front end
surface and the main pole end surface in the down track direction
protrudes toward the magnetic recording medium.
[0015] The magnetic head slider approaches a predetermined position
of the magnetic recording medium from the leading side, and
subsequently, the trailing side approaches. According to the
present invention, at least a portion of laser light that is not
coupled with the plasmon generator thermally deforms the air
bearing surface. At this time, at least a part of the air bearing
surface positioned closer to the leading side than the generator
front end surface and the main pole end surface in the down track
direction protrudes toward the magnetic recording medium.
Consequently, the convex part of the air bearing surface makes
contact with this protrusion part first and deforms, and the height
of the convex part is reduced. After that, the convex part of the
air bearing surface approaches the generator front end surface of
the plasmon generator; however, since the height of the convex part
is reduced, a collision can be avoided, or even if a collision
occurs, the impact force decreases. Therefore, the possibility that
the heat and mechanical stress are applied to the generator front
end surface of the plasmon generator due to contact with the
magnetic recording medium is reduced, and the agglomeration of the
generator front end surface is suppressed.
[0016] Another embodiment of the present invention provides a
manufacturing method for a TAMR head mentioned above. The present
manufacturing method targets a predetermined positional
relationship between a laser beam generator and a magnetic head
slider, and includes affixing the laser diode unit including the
laser light generator to the magnetic head slider. In the
positional relationship described above, a portion of the laser
light is coupled with the core, and the emission center of the
laser light generator is shifted toward the leading side in the
down track direction from the position with the highest coupling
efficiency to the core.
[0017] The above mentioned or other objective, characteristics and
advantages of the present invention will become clear from the
following explanation by referring to the attached drawings where
the present invention is exemplified.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is an overall perspective view of a thermal assisted
magnetic recording head;
[0019] FIG. 2 is a conceptual cross-sectional view of a thermal
assisted magnetic recording head relating to one embodiment of the
present invention;
[0020] FIG. 3 is a schematic cross-sectional view of a plasmon
generator, a core, a main pole and a leading shield;
[0021] FIGS. 4A to 4C are views showing a relationship between an
offset of a laser diode and a distribution of uncoupled light,
respectively;
[0022] FIGS. 5A to 5B are schematic views showing the problem when
the plasmon generator protrudes more than the leading shield,
respectively;
[0023] FIGS. 6A to 6C are schematic views showing the effect when
the leading shield protrudes more than the plasmon generator,
respectively;
[0024] FIGS. 7A to 7C are schematic views showing the effect when
the plasmon generator protrudes slightly more than the leading
shield, respectively;
[0025] FIG. 8 is a perspective view of the core relating to another
embodiment of the present invention;
[0026] FIG. 9 is a graph showing the measured values of the
protrusion amounts of the main pole and the leading shield;
[0027] FIG. 10 is a graph showing the relationship between the
offset of the laser diode and the longevity of the magnetic
head;
[0028] FIG. 11 is a graph showing the relationship between the
offset of the laser diode and the necessary electric current of the
laser diode;
[0029] FIG. 12 is a perspective view of the head arm assembly of
the present invention;
[0030] FIG. 13 is a side view of the head stack assembly of the
present invention; and
[0031] FIG. 14 is a plan view of the magnetic recording device of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0032] First, a configuration of a thermal assisted magnetic
recording head relating to one embodiment of the present invention
is explained. FIG. 1 is an overall perspective view of the TAMR
head. FIG. 2 is an overall cross-sectional view of the TAMR head
cut along the line 2-2 of FIG. 1. FIG. 3 is a cross-sectional view
cut along the line 2-2 of FIG. 1, schematically showing the plasmon
generator, the core, the main pole and the leading shield.
[0033] In the specification, the x direction refers to the down
track direction (recording medium circumferential direction) or a
direction that is orthogonal to an integrated surface 3a of a
substrate 3 where a magneto resistive (MR) element and a magnetic
recording element are formed; the y direction refers to the cross
track direction (recording medium radius direction) of the magnetic
recording medium 14; and the z direction refers to the direction
that is orthogonal to the air bearing surface of a magnetic head
slider. The x direction corresponds to the film formation direction
L in the wafer process, the relative movement direction of the
magnetic head slider with respect to the track circumferential
direction of the magnetic recording medium 14, or a tangential
direction of a track at a position of the thermal assisted magnetic
recording head on the magnetic recording medium 14. The x
direction, the y direction and the z direction are orthogonal to
each other. "Upward" and "downward" correspond to a direction away
from a substrate and a direction approaching the substrate relative
to the x direction, respectively. Instead of "upward," "trailing
side" may be used, and instead of "downward," "leading side" may be
used.
[0034] A magnetic head 1 has a magnetic head slider 2, and a laser
diode unit 31 that is affixed to the magnetic head slider 2 and
emits laser light.
[0035] The magnetic head slider 2 has a substantially hexahedral
shape, one surface of which configures an air bearing surface S
opposite to the magnetic recording medium 14. The magnetic head
slider 2 has an MR element 4, a magnetic recording element 5, a
waveguide 17 that includes a core 15 that can propagate laser light
emitted from the laser diode unit 31 as propagating light, and a
plasmon generator 16 that generates NF light at the air bearing
surface S from the propagating light. These elements are formed on
a substrate 3 made of AlTiC (Al.sub.2O.sub.3--TiC).
[0036] The magnetic recording element 5 has a main pole 10 for
perpendicular magnetic recording facing the air bearing surface S.
The main pole 10 is provided adjacent to the plasmon generator 16.
A main pole end surface 10a, which is an end part of the main pole
10, is positioned on the air bearing surface S, and generates a
magnetic field for recording at the air bearing surface S. A
leading shield 11 is provided at the leading side of the main pole
10 in the down track direction x. The leading shield 11 is
magnetically linked with the main pole 10 via a contact part 12,
and configures an integrated magnetic circuit with the main pole
10. The main shield 11 has a shield end surface 11a facing the air
bearing surface S. Coils 13a and 13b are wound around the main pole
10 to set the contact part 12 as the center. The main pole 10, the
leading shield 11 and the contact part 12 are formed with an alloy
made of any two or three of Ni, Fe and Co. An overcoat layer 25
made of Al.sub.2O.sub.3 is provided upward in the x direction of
the magnetic recording element 5.
[0037] Magnetic flux generated inside the main pole 10 is emitted
from the main pole end surface 10a toward the magnetic recording
medium 14 as magnetic flux for writing. The magnetic flux emitted
from the main pole end surface 10a enters into the magnetic
recording medium 14 and magnetizes each recording bit in the
perpendicular direction z. The magnetic flux changes its magnetic
path to the in-plane direction (x direction), again changes its
orientation to the perpendicular direction (z direction) in the
vicinity of the leading shield 11, and is then absorbed by the
leading shield 11 from the shield end surface 11a.
[0038] The magnetic head slider 2 has a waveguide 17 that can
propagate laser light. The waveguide 17 includes the core 15
extending in the z direction and a cladding 18 covering the core
15. The core 15 propagates laser light generated at the laser diode
unit 31 in the z direction as propagating light 40. The core 15
extends from the end part 15a (incident end surface of laser light)
opposite to the laser diode unit 31 of the magnetic head slider 2
to the air bearing surface S or its vicinity. The core 15 may
terminate before the air bearing surface S or may extend to the air
bearing surface S. The cross section of the core 15 that is
orthogonal to the propagation direction (z direction) of the
propagating light 40 is rectangular, and its width (dimension in
the y direction) is greater than its thickness (dimension in the x
direction). The core 15 may be formed with, for example, TaOx. TaOx
means tantalum oxide with any composition, of which
Ta.sub.2O.sub.5, TaO, TaO.sub.2 and the like are typical, but is
not limited to these. The core 15 is covered with the cladding 18
having a smaller refractive index than the core 15. The cladding 18
can be formed with a dielectric body, for example, SiO.sub.2,
Al.sub.2O.sub.3 and the like.
[0039] The magnetic head slider 2 has an MR element 4, the front
end part of which is positioned on the air bearing surface S, and
the upper-side shield layer 6 and the lower-side shield layer 7
that are respectively provided at both sides of the MR element 4 in
the x direction. The MR element 4 may be any of a Current-in-Plane
(CIP)-Gigantic-Magneto-Resistive (GMR) element where its sense
current flows in they direction, a Current-Perpendicular-to-Plane
(CPP)-GMR element where its sense current flows in the x direction
or a Tunneling-Magneto-Resistive (TMR) element where its sense
current flows in the x direction, and that utilizes a tunnel
effect. When the MR element 4 is the CPP-GMR element or the TMR
element, the upper-side shield layer 6 and the lower-side shield
layer 7 are also utilized as electrodes that supply a sense
current. A magnetic shield layer 8 is provided between the MR
element 4 and the magnetic recording element 5.
[0040] The magnetic head slider 2 has a plasmon generator 16 that
generates NF light at the air bearing surface S from the
propagating light 40. The plasmon generator 16 includes a generator
front end surface 16a facing the air bearing surface S, and extends
to the generator front end surface 16a opposite to a part of the
core 15 along the core 15. The main pole end surface 10a is
positioned in the vicinity of the generator front end surface 16a.
The plasmon generator 16 is coupled with a portion of the
propagating light 40 that propagates through the core 15 in the
surface plasmon mode and generates surface plasmon, propagates the
surface plasmon to the generator end surface 16a, generates NF
light at the generator front end surface 16a and irradiates the NF
light to the magnetic recording medium 14. With this, the plasmon
generator 16 heats the portion of the magnetic recording medium 14
where information is recorded. The plasmon generator 16 is formed
with Au, Ag, Cu, Al, Pd, Ru, Pt, Rh, Ir or an alloy that consists
primarily of these metals.
[0041] In the present embodiment, the plasmon generator 16 is a
roughly quadrangular prism shaped metallic strip having a
rectangular cross section. Therefore, the generator front end
surface 16a is rectangular; however, it may also be square,
triangular or the like. Out of four sides of the plasmon generator
16 extending in the z direction, a surface opposite to the core 15
configures a propagation surface 16b. The propagation surface 16b
is coupled with the propagating light 40 that propagates through
the core 15 in the surface plasmon mode, and generates surface
plasmon SP. The propagation surface 16b propagates the generated
surface plasmon SP to the generator front end surface 16a of the
plasmon generator 16, and generates NF light at the generator front
end surface 16a.
[0042] The laser diode unit 31 is positioned opposite to a surface
on the opposite side of the air bearing surface S of the magnetic
head slider 2. The laser diode unit 31 emits laser light toward the
core 15 of the waveguide 17 of the magnetic head slider 2 in the
direction z that is perpendicular to the air bearing surface S. The
laser diode unit 31 is soldered to the magnetic head slider 2 by a
bonding layer 37.
[0043] The laser diode unit 31 includes a laser diode 32, which is
a laser light generator, and a sub mount 33 where the laser diode
32 is mounted. The laser diode 32 supplies laser light to the core
15. The sub mount 33 is made of a Si substrate and the like. The
laser diode 32 is mounted onto the mounting surface 33a of the sub
mount 33. Specifically, a first electrode (p electrode) 32j of the
laser diode 32 is affixed to a pad 41 that is provided at the
mounting surface 33a of the sub mount 33 with a solder material
42.
[0044] The laser diode 32 is an edge emitting type, and one that is
normally used for communication, such as an InP-system, a
GaAs-system or a GaN-system, for optical system disk storage or for
material analysis. The wavelength of the laser light to be emitted
is not particularly limited, but a wavelength in the range of 375
nm to 1.7 .mu.m can be utilized, and in particular, a wavelength of
approximately 650 to 900 nm is preferably used.
[0045] The laser diode 32 is not limited to the following
configuration, but in one example, it has a configuration in which
an n electrode 32a configuring a second electrode, an n-GaAs
substrate 32b, an n-InGaAlP cladding layer 32c, a first InGaAlP
guide layer 32d, an active layer 32e made of a multiple quantum
well (InGaP/InGaAlP), a second InGaAlP guide layer 32f, a p-InGaAlP
cladding layer 32g, a p electrode under layer 32h and the p
electrode 32j configuring the first electrode are sequentially
laminated. In front and behind a cleavage surface of the laser
diode 32, reflection layers 32k and 32l are formed for exciting the
oscillation by total reflection. The surface of the reflection
layer 32k, i.e. a surface opposite to the magnetic head slider 2 of
the laser diode 32, configures a light-emitting surface 32n of the
laser diode 32. An emission center 32m exists at the position of
the active layer 32e of the reflection layer 32k. The n electrode
32a and the p electrode 32j can be formed with Au or an Au alloy
with a thickness of approximately 0.1 .mu.m. When a hard disk
device is operated, electricity is supplied to the laser diode 32
from the power source inside the hard disk device via the first
electrode 32j and the second electrode 32a.
[0046] With reference to FIG. 3, in the present embodiment, the
emission center 32m of the laser diode 32 is shifted toward the
leading side in the down track direction x from the center position
15b of the down track direction of the core 15. The magnitude of
the shift, i.e., the offset DT toward the down track direction x,
is defined as shown in FIG. 3. When the offset DT=0, a laser light
44 is coupled with the core 15 at the highest coupling efficiency.
In other words, when the offset DT=0, the laser light is introduced
into the core 15 with the highest rate of optical energy of the
laser light 44 emitted from the laser diode 32. In the position
where the offset DT=0, the center of the optical distribution of
the laser light 44 emitted from the laser diode 32 is normally on
an extended line 15e of a central axis 15c of the core 15. In the
specification, when the emission center 32m of the laser diode 32
is shifted toward the trailing side (i.e., the main pole 10 side)
from the standard position where the offset DT=0, the offset DT is
regarded as positive, and when it is shifted toward the leading
side (i.e. leading shield 11 side), the offset DT is regarded as
negative. FIG. 3 shows the negative offset DT. The magnitude of the
offset DT, i.e. the offset distance DT between the emission center
32m of the laser diode 32 and the central axis 15c of the core in
the down track direction, is desirably within the range of 0 to
37.5% (excluding 0%) of a down track-direction dimension 15d of the
core 15 (thickness of the core 15 in the x direction).
[0047] As schematically shown in FIG. 3, the laser light 44 emitted
from the laser diode 32 diffuses from the emission center 32m and
propagates in the air. A portion of the laser light 44 is
irradiated toward the incident end surface 15a of the core 15, is
coupled with the core 15, propagates inside the core 15 as the
propagating light 40, and generates plasmon at the plasmon
generator 16 (furthermore, the propagating light 40 in the figure
is represented by a curved line for convenience in order to express
coupling with the plasmon generator 16). Residual laser light 43 is
primarily irradiated to the cladding 18 positioned on the leading
side of the core 15, and propagates inside the cladding 18 without
being coupled with the core 15 as propagating light. In the
specification, laser light that is not coupled with the core 15 as
propagating light or light that leaks to the cladding 18 without
being coupled with the core 15 is referred to as uncoupled
light.
[0048] FIGS. 4A to 4C show intensity distributions of the uncoupled
light when the offset DT is negative (-0.6 .mu.m), 0 and positive
(+0.6 .mu.m), respectively. The darker portion indicates higher
light intensity, and the lighter portion indicates lower light
intensity. In FIG. 4A, since the irradiation range of the laser
light is shifted toward the leading side, the higher light
intensity appears on the lower side (leading side) of the core 15.
In FIG. 4B, since the irradiation range of the laser light is
symmetrical relative to the center of the core 15, the higher light
intensity appears almost symmetrically on the lower side (leading
side) and the upper side (trailing side) of the core 15. However,
since most of the laser light is coupled with the core 15, the
intensity of the uncoupled light is small. In FIG. 4C, since the
irradiation range of the laser light is shifted toward the trailing
side, the higher light intensity appears on the upper side
(trailing side) of the core 15. In the present embodiment, since
the emission center 32m of the laser diode 32 is positioned on the
leading side from the central axis of the core 15, the uncoupled
light is unevenly distributed on the leading side of the core 15.
In other words, the present embodiment produces the state shown in
FIG. 4A or a similar state.
[0049] The uncoupled light 43 propagating inside the cladding 18
reaches the vicinity of the leading shield 11 and heats the leading
shield 11. Consequently, the leading shield 11 protrudes toward the
magnetic recording medium 14 due to thermal expansion (shown in
FIG. 3 with a broken line). A structure other than the leading
shield 11, for example, an Al.sub.2O.sub.3 layer covering the
periphery of the leading shield 11, is also heated, and protrudes
toward the magnetic recording medium 14 due to thermal expansion.
Therefore, at least a portion of the uncoupled light 43 thermally
deforms the air bearing surface S so that a part of the air bearing
surface positioned closer to the leading side than the generator
front end surface 16a and the main pole end surface 10a in the down
track direction protrudes toward the magnetic recording medium 14.
Preferably, a part of the air bearing surface S (typically, the
shield end surface 11a of the leading shield 11) positioned on the
leading side protrudes more toward the magnetic recording medium 14
than the generator front end surface 16a of the plasmon generator.
16 and the main pole end surface 10a of the main pole 10.
[0050] For the reasons below, it is advantageous that the leading
shield 11 protrudes more toward the magnetic recording medium 14
than the plasmon generator 16 and the main pole 10. Asperities
exist on the magnetic recording medium 14 at a certain probability,
and a convex part collides with the air bearding surface S of the
magnetic head slider 2 with a certain probability. FIGS. 5A and 5B
schematically show the state in which a convex part 51 on the
rotating magnetic recording medium 14 approaches the magnetic head
and collides with the magnetic head. FIGS. 5A and 5B show the case
when the offset is positive, and the main pole 10 and the plasmon
generator 16 protrude more toward the magnetic recording medium 14
than the leading shield 11. The plasmon generator 16 accompanies
(is pulled by) the main pole 10, and protrudes toward the magnetic
recording medium 14 (FIG. 5A).
[0051] When the convex part 51 is within a certain height range,
the convex part 51 approaches the plasmon generator 16 without
colliding with the leading shield 11. Consequently, the convex part
51 directly collides against the plasmon generator 16 (FIG. 5B). At
this time, great stress and high temperature are instantaneously
generated, and the plasmon generator is deformed. This deformation
causes the agglomeration on the generator front end surface 16a of
the plasmon generator 16. In actuality, in a longevity test
described later, examining a magnetic head with a deteriorated S/N
ratio, markings indicating physical collisions were confirmed. Even
when the convex part 51 does not collide with the plasmon generator
16, but collides with the main pole 10, stress and high temperature
occurring at the main pole 10 propagate to the plasmon generator
16, and the plasmon generator 16 receives a similar impact when the
convex part 51 directly collides with the plasmon generator 16.
Therefore, it is also desirable to avoid a mechanical collision
between the main pole 10 and the convex part 51.
[0052] FIGS. 6A to 6C show the case when the offset is negative,
and the leading shield 11 protrudes more than the main pole 10 and
the plasmon generator 16. The convex part 51 collides with the
leading shield 11, is deformed on that occasion, and its height
becomes shorter. In other words, the leading shield 11 becomes a
sacrificial part and collides with the convex part 51, and the
magnetic recording medium 14 is substantially planarized (FIG. 6B).
Then, the convex part 51 approaches the plasmon generator 16, but
passes through the magnetic head without colliding with the plasmon
generator 16 and the main pole 10 (FIG. 6C). Because the leading
shield 11 collides with the convex part 51 first, direct physical
contact between the convex part 51 and the plasmon generator 16 is
avoided. Consequently, it is difficult to generate agglomeration on
the generator front end surface 16a of the plasmon generator 16,
and thermal reliability of the plasmon generator 16 is
enhanced.
[0053] It is effective that the leading shield 11 protrudes more
than the main pole 10 and the plasmon generator 16 even in the
`touchdown` process to determine a reference point for
determination of clearance between the head and the magnetic
recording medium. The touchdown process is conducted during the
operation of the magnetic recording device in order to maintain the
clearance within the optimum range. In this process, by activating
a flexure, the magnetic head is moved up and down with respect to
the magnetic recording medium 14. During this process, the magnetic
head collides with the magnetic recording medium 14. In order to
accurately determine the reference point, it is necessary to
accurately detect the collision. In general, the leading shield 11
has a greater area to make contact with the magnetic recording
medium 14 than the main pole 10 and the plasmon generator 16, so a
signal in association with such contact is easily detected.
[0054] FIGS. 7A to 7C show cases when the offset is positive but
the offset value is small, and the main pole 10 and the plasmon
generator 16 protrude slightly more than the leading shield 11
(FIG. 7A). As similar to FIG. 6B, the convex part 51 collides with
the leading shield 11, and is deformed on that occasion, and the
height becomes shorter. In other words, the leading shield 11
becomes a sacrificial part and collides with the convex part 51,
and the medium is substantially planarized (FIG. 7B). Then, the
convex part 51 collides with the plasmon generator 16, but because
the height of the convex part 51 becomes shorter, the impact force
is small, and great stress and high temperature at the plasmon
generator 16 do not occur (FIG. 7C).
[0055] In the present invention, it is the most preferable that the
leading shield 11 protrudes more than the main pole 10 and the
plasmon generator 16, but it is also effective when the leading
shield 11, the main pole 10 and the plasmon generator 16 protrude
equally, or even when the main pole 10 and the plasmon generator 16
protrude slightly more than the leading shield 11. As shown in
examples, when the main pole 10 protrudes approximately 2 nm more
than the leading shield 11, the effect of the present invention can
be obtained.
[0056] It is believed that contamination that is adhered onto the
magnetic recording medium 14 functions similarly to the asperity of
the magnetic recording medium 14. Therefore, an effect of the
contamination can be reduced by causing the leading shield 11 to
protrude by utilizing the uncoupled light.
[0057] The air bearing surface can be also thermally expanded using
propagating light, which is coupled with the core 15 but not
coupled with the plasmon generator 16. A core 115 shown in FIG. 8
has a first part 115a that includes an incident end surface 115d of
laser light, and where its width in the cross track direction y is
wider, a second part 115b that includes a part opposite to the
plasmon generator 16, and where its width in the cross track
direction y is narrower, and a third part 115c that links the first
part 115a and the second part 115b, and where its width in the
cross track direction y changes in the direction z that is
orthogonal to the air bearing surface S. The third part 115c
selectively propagates light 40a in a low-order mode that is
required for generating NF light, and leaks light 40b in a
high-order mode, which is not selected, from the third part 115c of
the core 115. The light 40b in the high-order mode propagates
through the cladding, and heats the leading shield 11. It is also
possible to leak the light in high-order mode from the core not by
changing a shape of the core but by changing a material of the core
along the axis of the core in the z direction.
[0058] The TAMR head of the present embodiment can be created with
the following steps. [0059] (1) On a wafer (substrate 3), the
lower-side shield layer 7 is formed by a plating method, the MR
element 4 is formed by sputtering and the upper-shield layer 6 is
formed by a plating method. [0060] (2) The magnetic shield layer 8
is formed by the plating method. [0061] (3) The leading shield 11
is formed by the plating method. [0062] (4) The waveguide 17 made
of a three-layer structure of the cladding 18/the core 15/the
cladding 18 is formed by sputtering. [0063] (5) The plasmon
generator 16 is formed by sputtering. [0064] (6) The main pole 10
is formed by the plating method. [0065] (7) The overcoat layer 25
is formed by sputtering. [0066] (8) Many magnetic head sliders 2
are created by cutting the wafer. [0067] (9) The laser diode unit
31 is positioned relative to the core 15 so that laser light
couples with the core 15, and the laser diode unit 31 is adhered to
the magnetic head slider 2.
[0068] In Step (9), the laser diode unit 31 is adhered to the
magnetic head slider 2 so that the emission center 32m of the laser
diode 32 is shifted toward the leading side from the center of the
core 15. When the laser diode unit 31 is adhered to the magnetic
head slider 2, the position in the down track direction varies
because of errors in the detecting of a target position and errors
in the affixing of the laser diode unit 31. These errors are minute
errors that occur with a standard deviation of approximately 0.1 to
1 .mu.m, but they inevitably occur. Therefore, when the laser diode
unit 31 is adhered to the magnetic head slider 2, it is necessary
to consider these errors. For example, even if the laser diode unit
31 is adhered to the magnetic head slider 2 so that the emission
center 32m of the laser diode 32 is shifted toward the leading side
from the center of the core 15 by 0.3 .mu.m, the offset of -0.3
.mu.m cannot always be obtained. However, an offset within a
desired range can be obtained by targeting the positional
relationship between the laser diode unit 31 and the magnetic head
slider 2 to obtain -0.3 .mu.m of offset. Therefore, the laser diode
unit 31 can be affixed to the magnetic head slider 2 by targeting
to have a positional relationship where a portion of the laser
light is coupled with the core 15, and the emission center 32m of
the laser diode 32 is shifted toward the leading side in the down
track direction from a position with the highest coupling
efficiency to the core 15 by any desired offset distance.
Example
[0069] In accordance with the steps above, a magnet slider was
created. The down track-direction dimension 15d of the core 15 was
400 nm. In Step (9), the laser diode unit 31 was shifted in the
down track direction by various distances, and was adhered to the
magnetic head slider.
[0070] A current was passed to the magnetic head slider that was
created as described above, laser light was irradiated to the core
15 from the laser diode 32, and protrusion distances of the main
pole 10 and the leading shield 11 in the direction z orthogonal to
the air bearing surface were measured. The results are shown in
FIG. 9. The horizontal axis indicates the offset DT in the down
track direction, and the vertical axis indicates a protrusion
distance of the leading shield 11 with respect to the main pole 10.
When the offset is positive, it indicates that the main pole 10
protrudes more than the leading shield 11, and when the offset is
negative, the leading shield 11 protrudes more than the main pole
10. It is assumed that this is because an uncoupled light that is
not coupled with the core mainly exists on the leading shield 11
side when the offset is negative, the uncoupled light heats the
leading shield 11 and the leading shield 11 protrudes more than the
main pole 10. Inversely, it is assumed that this is because the
uncoupled light exists mainly on the trailing side when the offset
is positive, and a structure in the vicinity of the main pole 10 is
heated, and the main pole 10 protrudes more than the leading shield
11. As described above, the shape of the air bearing surface that
greatly affects a flying posture, and particularly distribution of
the protrusion distance in the direction that is orthogonal to the
air bearing surface, can be controlled by adjusting the offset.
[0071] Next, the longevity of the magnetic head created as
described above was measured. The longevity is defined as a
recorded time required for the SN ratio of the recording pattern
recorded in the magnetic recording medium 14 to be decreased by 2
dB. As shown in FIG. 10, when the offset is negative, i.e., when
the leading shield 11 protrudes more than the main pole 10, it was
ascertained that the longevity is increased.
[0072] In the meantime, as an absolute value of the offset
increases, the coupling efficiency to the core of the laser light
that is emitted from the laser diode unit decreases. Consequently,
a supply current to the laser diode unit required for thermal
assist recording increases. FIG. 11 shows a supply current to the
laser diode required for heating the magnetic recording medium 14
to predetermined temperature as a function of the offset DT. When
the offset is either positive or negative, when the offset is 0.6
.mu.m or greater, a necessary electric current exceeds 70 mA, and
is not preferable from a reliability standpoint of the laser diode
unit itself.
[0073] According to the results above, in the system that was used
as the example, it is preferable that the offset is within the
range of -0.45 .mu.m to +0.15 .mu.m, and taking the variation upon
the adhesion of the laser diode unit into consideration, the TAMR
head with the highest reliability can be obtained by setting the
offset of -0.15 .mu.m as the center. As described above, since the
down track-direction dimension 15d of the core 15 is 400 nm, it is
desirable that the offset is distributed within a range of
thickness 15d of the core 15 of .+-.75% setting the position
shifted toward the leading side from the central axis 15c by the
distance that is equivalent to 37.5% of the thickness 15d of the
core 15 as the center. In other words, the offset is preferably
distributed within the range of -112.5% to +37.5% of the thickness
15d of the core 15 with respect to the central axis 15c of the core
15. This range of the offset is equivalent to the case when the
leading shield 11 protrudes to a level (.+-.2 nm) equal to the main
pole 10. Consequently, it is believed that the increased longevity
as shown in FIG. 10 can be observed.
[0074] Next, a head gimbal assembly (HGA) where the thermal
assisted magnetic recording head is mounted is explained.
[0075] With reference to FIG. 12, a head gimbal assembly (HGA) 220
includes the thermal assisted magnetic recording head 1 and a
suspension 221 that elastically supports the thermal assisted
magnetic recording head 1. The suspension 221 has a plate
spring-state load beam 22 formed with stainless steel, a flexure
223 provided at one end part of the load beam 222, and a base plate
224 provided at the other end part of the load beam 222. The
thermal assisted magnetic recording head 1 is joined to the flexure
223, and provides an appropriate degree of freedom to the thermal
assisted magnetic recording head 1. A gimbal part for keeping the
position of the thermal assisted magnetic recording head 1 constant
is provided at the portion where the thennal assisted magnetic
recording head 1 is attached.
[0076] The assembly that the HGA 220 is mounted to an arm 230 is
referred to as a head arm assembly 221. The arm 230 moves the
thermal assisted magnetic recording head 1 in the cross track
direction y of the magnetic recording medium 14. A base plate 224
is attached to one end of the arm 230. A coil 231, which is a part
of a voice coil motor, is attached to the other end part of the arm
230. A bearing part 233 is provided in the intemiediate part of the
arm 230. The arm 230 is rotatably supported by a shaft 234 attached
to the bearing part 233. The arm 230 and the voice coil motor that
drives the arm 230 configure an actuator.
[0077] Next, with reference to FIG. 13 and FIG. 14, a head stack
assembly in which the thermal assisted magnetic recording head 1 is
incorporated and a magnetic recording device are explained. The
head stack assembly is an assembly where the HGA 220 is attached to
each arm of a carriage having a plurality of aims. FIG. 13 is a
side view of the head stack assembly, and FIG. 14 is a plan view of
the magnetic recording device. The head stack assembly 250 has a
carriage 251 having a plurality of arms 230. The HGA 220 is
attached to each arm 230 so as to be spaced from each other and
arranged side-by-side in a perpendicular direction. A coil 253,
which is a part of the voice coil motor, is attached to the
opposite side of the arm 230 of the carriage 251. The voice coil
motor has permanent magnets 263 arranged at opposite positions
across the coil 253.
[0078] With reference to FIG. 13, the head stack assembly 250 is
incorporated into a magnetic recording device 260. The magnetic
recording device 260 has a plurality of the magnetic recording
media 14 that are attached to a spindle motor 261. Two thermal
assisted magnetic recording heads 1 are arranged to be opposite in
every magnetic recording medium 14 across the magnetic recording
medium 14. The head stack assembly 250 except for the thermal
assisted magnetic recording heads 1 and the actuator correspond to
a positioning device, support the thermal assisted magnetic
recording heads 1, and, position the thermal assisted magnetic
recording heads 1 with respect to the magnetic recording medium 14.
The thermal assisted magnetic recording heads 1 are moved in the
cross track direction of the magnetic recording medium 14 by the
actuator, and are positioned with respect to the magnetic recording
medium 14. The thermal assisted magnetic recording head 1 records
information into the magnetic recording medium 14 by the magnetic
recording element 5, and reproduces the information recorded in the
magnetic recording medium 14 by the MR element 4.
[0079] Although the desired embodiments of the present invention
were presented and explained in detail, as long as they do not
depart from the effect or the scope of attached claims, readers
should understand that various modifications and amendments are
possible.
* * * * *