U.S. patent application number 14/277374 was filed with the patent office on 2015-11-19 for thermal assisted magnetic recording head with protrusion on leading side of plasmon generator.
This patent application is currently assigned to TDK Corporation. The applicant listed for this patent is SAE Magnetics (H.K.) Ltd., TDK Corporation. Invention is credited to Ryuji FUJII, Yasutoshi FUJITA, Kenta HARA, Tetsuya ROPPONGI, Kosuke TANAKA.
Application Number | 20150332717 14/277374 |
Document ID | / |
Family ID | 54434657 |
Filed Date | 2015-11-19 |
United States Patent
Application |
20150332717 |
Kind Code |
A1 |
HARA; Kenta ; et
al. |
November 19, 2015 |
THERMAL ASSISTED MAGNETIC RECORDING HEAD WITH PROTRUSION ON LEADING
SIDE OF PLASMON GENERATOR
Abstract
A thermal assisted magnetic recording head of the present
invention has an air bearing surface (ABS) 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 ABS, and a main pole that faces the
ABS and emits magnetic flux to the magnetic recording medium. The
plasmon generator is opposite to a part of the core and extends to
the generator front surface, is coupled with a portion of the
propagating light that propagates through the core in the surface
plasmon mode to generate a 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
irradiate the NF light to the magnetic recording medium. The ABS
has a protrusion that is closer to the leading side than the
generator front end surface in the down track direction, and that
protrudes more toward the magnetic recording medium than the
generator front end surface upon operation of the thermal assisted
magnetic recording head.
Inventors: |
HARA; Kenta; (Tokyo, JP)
; TANAKA; Kosuke; (Tokyo, JP) ; ROPPONGI;
Tetsuya; (Tokyo, JP) ; FUJII; Ryuji; (Hong
Kong, CN) ; FUJITA; Yasutoshi; (Hong Kong,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TDK Corporation
SAE Magnetics (H.K.) Ltd. |
Tokyo
Hong Kong |
|
JP
CN |
|
|
Assignee: |
TDK Corporation
Tokyo
JP
SAE Magnetics (H.K.) Ltd.
Hong Kong
CN
|
Family ID: |
54434657 |
Appl. No.: |
14/277374 |
Filed: |
May 14, 2014 |
Current U.S.
Class: |
369/13.33 ;
29/603.07; 29/603.16 |
Current CPC
Class: |
G11B 2005/0021 20130101;
G11B 5/314 20130101; Y10T 29/4905 20150115; G11B 5/3106 20130101;
Y10T 29/49034 20150115; G11B 5/4866 20130101; G11B 5/3169 20130101;
G11B 5/1278 20130101; G11B 5/6082 20130101; G11B 5/6088
20130101 |
International
Class: |
G11B 5/48 20060101
G11B005/48; G11B 5/31 20060101 G11B005/31; G11B 5/60 20060101
G11B005/60 |
Claims
1. A thermal assisted magnetic recording head, comprising: an air
bearing surface (ABS) 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
ABS, and a main pole that faces the ABS and emits magnetic flux to
the magnetic recording medium, wherein the plasmon generator is
opposite to a portion 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
to 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 irradiate the magnetic
recording medium, and the ABS comprises a protrusion that is closer
to the leading side than the generator front end surface in the
down track direction, and that protrudes more toward the magnetic
recording medium than the generator front end surface when the
thermal assisted magnetic recording head is operated.
2. The thermal assisted magnetic recording head according to claim
1, wherein the protrusion protrudes more than the generator front
end surface by 0.5 to 2 .mu.m.
3. The thermal assisted magnetic recording head according to claim
1, wherein the core is positioned closer to the leading side in the
down track direction than the plasmon generator, and the protrusion
is separated by a distance, which is no less than an interval
between the plasmon generator and the core, in the down track
direction from the generator front end surface.
4. The thermal assisted magnetic recording head according to claim
1, wherein the protrusion is situated at a position of 0.03 to 3
.mu.m in the down track direction from the generator front end
surface.
5. The thermal assisted magnetic recording head according to claim
1, wherein the protrusion has a length of 15 .mu.m or more in the
cross track direction.
6. The thermal assisted magnetic recording head according to claim
1, wherein the protrusion has a length of 100 .mu.m or less in the
cross track direction.
7. The thermal assisted magnetic recording head according to claim
1, wherein the protrusion has a Mobs hardness of 5 or more.
8. The thermal assisted magnetic recording head according to claim
7, wherein the protrusion is diamond, diamond-like carbon, boron
nitride, titanium, vanadium, chrome, zinc, neodymium, molybdenum,
hafnium, tantalum, tungsten, or an oxide or nitride thereof.
9. The thermal assisted magnetic recording head according to claim
1, wherein the protrusion passes on a surface of the core opposite
to the magnetic recording medium, and extends on both sides of the
surface opposite to the magnetic recording medium in the cross
track direction.
10. The thermal assisted magnetic recording head according to claim
1, further comprising: a leading shield that is positioned closer
to the leading side than the plasmon generator, that is
magnetically coupled with the main pole, that has a shield end
surface facing the ABS, and that absorbs magnetic flux returning
from the magnetic recording medium at the shield end surface,
wherein the leading shield comprises a chamfer that faces the
plasmon generator and the magnetic recording medium, and that
extends in the cross track direction, and the protrusion extends on
the chamfer.
11. The thermal assisted magnetic recording head according to claim
1, further comprising: a leading shield that is positioned closer
to the leading side than the plasmon generator, that is
magnetically coupled with the main pole, that has a shield end
surface facing the ABS, and that absorbs magnetic flux returning
from the magnetic recording medium at the shield end surface,
wherein the protrusion is formed on the shield end surface.
12. The thermal assisted magnetic recording head according to claim
1, wherein the protrusion comprises a smaller milling rate or a
smaller polishing rate, or both, than other parts configuring the
ABS.
13. 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.
14. A magnetic recording device, comprising: the thermal assisted
magnetic recording head according to claim 1, the magnetic
recording medium that is positioned opposite to the thermal
assisted magnetic recording head, 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.
15. A manufacturing method for a thermal assisted magnetic
recording head that comprises an air bearing surface (ABS) 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 ABS, and a main pole that
faces the ABS and emits magnetic flux to the magnetic recording
medium, wherein the plasmon generator is opposite to a portion 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 to 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 irradiate the magnetic recording medium, the method
comprising: a step of forming the ABS so as to include a protrusion
that is closer to the leading side than the generator front end
surface in down track direction, and that protrudes more toward the
magnetic recording medium than the generator front end surface when
the thermal assisted magnetic recording head is operated.
16. The manufacturing method for a thermal assisted recording head
according to claim 15, further comprising the steps of: forming a
plurality of head sliders comprising the core, the plasmon
generator, the main pole and the protrusion, respectively, on a
wafer in a reticular pattern; cutting the wafer so as to allow a
surface facing the generator front end surface to be a cut plane
surface, and dividing into row bars including the plurality of
magnetic head sliders, or individual magnetic head sliders; and
forming the ABS by polishing and milling the cut plane surface,
wherein the protrusion comprises a smaller milling rate or a
smaller polishing rate, or both, than other parts configuring the
ABS.
17. The manufacturing method for a thermal assisted magnetic
recording head according to claim 15, further comprising the steps
of: forming a plurality of head sliders comprising the core, the
plasmon generator and the main pole, respectively, on a wafer in a
reticular pattern; cutting the wafer so as to allow the surface
facing the generator front end surface to be a cut plane surface,
and dividing into row bars including the plurality of magnetic head
sliders or individual magnetic head sliders; polishing and milling
the cut plane surface; and forming the protrusion on the polished
and milled cut plane surface.
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) to heat a magnetic recording
medium (NF light heating) are known.
[0008] As an example of direct heating, in JP H10-162444, 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 type perpendicular magnetic recording head is
disclosed. The NF light probe is a scatterer made of gold, and is
formed perpendicular to the magnetic recording medium contacting
the main pole.
[0011] One of the problems with 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 a
manufacturing method thereof.
SUMMARY OF THE INVENTION
[0014] The thermal assisted magnetic recording head of the present
invention has an air bearing surface (ABS) 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 ABS, and a main pole that faces the
ABS and emits magnetic flux to the magnetic recording medium. The
plasmon generator is opposite to a portion of the core and extends
to the generator front surface, is coupled with a portion of the
propagating light that propagates through the core in the surface
plasmon mode to generate a 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 irradiate
the NF light to the magnetic recording medium. The ABS has a
protrusion that is closer to the leading side than the generator
front end surface in the down track direction, and that protrudes
more toward the magnetic recording medium than the generator front
end surface upon operation of the thermal assisted magnetic
recording head.
[0015] The magnetic head slider of the thermal assisted magnetic
recording head makes contact with a recording medium due to
asperities of the ABS and the recording medium. Contact occurs at
the leading side of the ABS first, and then at the trailing side.
According to the present invention, the convex part of the ABS
makes contact with the protrusion, reducing the height of the
convex part. The convex part of the ABS then approaches the
generator front end surface of the plasmon generator; however,
since the height of the convex part is reduced, collision can be
avoided or the impact force is reduced even if collision occurs.
Therefore, because the heat generation on the generator front end
surface of the plasmon generator due to contact with the magnetic
recording medium is reduced and a possibility of deformation due to
the collision is reduced, agglomeration of the generator front end
surface is suppressed.
[0016] The above-mentioned objective and other objective(s),
characteristics and advantages of the present invention would be
clarified from the following explanation by referring to attached
drawings illustrating the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is an overall perspective view of the thermal
assisted magnetic recording head;
[0018] FIG. 2 is a conceptual cross-sectional view of a thermal
assisted magnetic recording head relating to one embodiment of the
present invention;
[0019] FIG. 3A is a conceptual cross-sectional view of main parts
of the thermal assisted magnetic recording head shown in FIG.
2;
[0020] FIG. 3B is a conceptual view showing an air bearing surface
(ABS) of the main parts of the thermal assisted magnetic recording
head shown in FIG. 3A;
[0021] FIGS. 4A to 4B are respective schematic views showing a
problem in the case when a plasmon generator protrudes;
[0022] FIGS. 5A to 5C are respective schematic views showing an
effect of the protrusion;
[0023] FIG. 6A is a conceptual cross-sectional view of main parts
of a thermal assisted magnetic recording head relating to another
embodiment;
[0024] FIG. 6B is a conceptual view showing the ABS of the main
parts of the thermal assisted magnetic recording head shown in FIG.
6A;
[0025] FIG. 7A is a conceptual cross-sectional view of the main
parts of a thermal assisted magnetic recording head relating to
another embodiment;
[0026] FIG. 7B is a conceptual view showing the ABS of the main
part of the thermal assisted magnetic recording head shown in FIG.
7A;
[0027] FIG. 8 is a perspective view of a head arm assembly of the
present invention;
[0028] FIG. 9 is a side view of a head stack assembly of the
present invention; and
[0029] FIG. 10 is a plan view of a magnetic recording device of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0030] First, a configuration of the thermal assisted magnetic
recording head relating to one embodiment of the present invention
is explained. FIG. 1 is an overall perspective view of the thermal
assisted magnetic recording head. FIG. 2 is an overall perspective
view of the thermal assisted magnetic recording head cut along the
line 2-2 of FIG. 1. FIG. 3A is a cross sectional view cut along the
line 2-2 of FIG. 1 schematically showing a plasmon generator, a
core, a main pole and a leading shield. FIG. 3B is a main part
schematic view of the ABS viewed from the line 3-3 of FIG. 3A.
[0031] In the specification, the x direction means a down track
direction, or a direction that is orthogonal to an integrated
surface 3a of a substrate 3 where a magneto resistive (MR) element,
a magnetic recording element and the like are formed, and
corresponds to a recording medium circumferential direction. The y
direction means a cross track direction of a magnetic recording
medium 14, and corresponds to a recording medium radius direction.
The z direction means a direction that is orthogonal to an air
bearing surface S of a magnetic head slider. The x direction is
matched with a film formation direction L in the wafer process. The
x direction, the y direction and the z direction are orthogonal to
each other. "Upward" and "downward" mean a direction away from a
substrate and a direction approaching the substrate relative to the
x direction, respectively. "Trailing side" may be used instead of
"upward", and "leading side" may be used instead of "downward".
[0032] 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.
[0033] The magnetic head slider 2 has substantially formed in a
hexahedral shape, one surface of which configures the 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 the substrate 3 made of ALTiC
(Al.sub.2O.sub.3--TiC).
[0034] The magnetic recording element 5 has a main pole 10 for
perpendicular magnetic recording that faces 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 along with the main
pole 10. The leading 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 of two or three of Ni, Fe and Co. An
overcoat layer 25 made of Al.sub.2O.sub.3 is provided upward of the
magnetic recording element 5 in the x direction.
[0035] 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) of the magnetic
recording medium 14, and again changes its orientation to the
perpendicular direction (z direction) in the vicinity of a leading
shield 11, and is then absorbed by the leading shield 11 from the
shield end surface 11a.
[0036] The magnetic head slider 2 has a waveguide 17 that can
propagate laser light. The waveguide 17 is positioned closer to the
leading side in the down track direction than the plasmon generator
16. The waveguide 17 has a 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 as propagating light 40
in the z direction. The core 15 extends from an end portion 15a
(incident end surface of laser beam) opposite to the laser diode
unit 31 of the magnetic head slider 2 to the vicinity of the air
bearing surface S. A cross section of the core 15 orthogonal to the
propagation direction (z direction) of the propagating light 40 is
rectangular, and the width (dimension in the y direction) is
greater than the 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, which has a smaller refractive index
than the core 15. The cladding 18 can be formed with a dielectric
body of, for example, SiO.sub.2, Al.sub.2O.sub.3 and the like.
[0037] The magnetic head slider 2 has an MR element 4, a front end
of which is positioned on the air bearing surface S, and an upper
part shield layer 6 and a lower part shield layer 7 that are
respectively provided at both sides of the MR element 4 in the x
direction. The MR element 4 is a reproducing element that reads
information recorded on the magnetic recording medium, and may be
any of a Current In Plane (CIP)--Gigantic Magneto Resistive (GMR)
element where a sense current flows in the y direction, a Current
Perpendicular to Plane (CPP)--GMR element where a sense current
flows in the x direction, and a Tunneling Magneto Resistive (TMR)
element where a sense current flows in the x direction and that
utilizes a tunnel effect. When the MR element 4 is a CPP-GMR
element or a 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.
[0038] 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 portion 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 to generate a surface plasmon, propagates the
surface plasmon to the generator front end surface 16a, and
generates NF light at the generator front end surface 16a to
irradiate the NF light to the magnetic recording medium 14. With
this, the plasmon generator 16 heats a 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, Jr or
an alloy that consists primarily of these metals.
[0039] 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 the 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 up to the generator front end surface 16a of the
plasmon generator 16 and generates the NF light at the generator
front end surface 16a.
[0040] The laser diode unit 31 is positioned opposite to the
surface of the magnetic head slider that in turn is opposite to the
air bearing surface S. The laser diode unit 31 emits laser light
toward the core 15 of the waveguide path 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.
[0041] The laser diode unit 31 includes a laser diode 32, which is
a laser light generating element, 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 a 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.
[0042] The laser diode 32 is an edge emitting type, and one that is
normally used for communication, for optical system disk storage or
for material analysis, such as an InP-series, a GaAs-series or a
GaN-series. Although the wavelength of the laser light to be
emitted is not particularly limited, a wavelength within the range
of 375 nm to 1.7 .mu.m can be utilized, and, in particular, a
wavelength around 650 to 900 nm is preferably used.
[0043] The laser diode 32 is not limited to the following
configuration, but in one example, it is configured such that 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 multiquantum well
(InGaP/InGaAlP), a second InGaAlP guide layer 32f, a p-InGaAlP
cladding layer 32g, a p electrode under layer 32h, and a p
electrode 32j configuring a first electrode are sequentially
laminated. Reflective layers 32k and 321 for exciting oscillation
due to total reflection are formed in front of and behind a
cleavage surface of the laser diode 32. A surface of the reflective
layer 32k, i.e., a surface of the laser diode 32 opposite to the
magnetic head slider 2 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 reflective 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 a light source inside the hard disk device via the first
electrode 32j and the second electrode 32a.
[0044] As shown in FIGS. 3A and 3B, the air bearing surface S has a
protrusion 19 that protrudes more toward the magnetic recording
medium 14 than the generator front end surface 16a at the time of
operating the thermal assisted magnetic recording head. The
protrusion 19 is provided closer to the leading side than the
generator front end surface 16a in the down track direction, and in
the present embodiment, the protrusion 19 passes on a surface 15a
of the core 15 opposite to the magnetic recording medium 14, and
extends on both sides of the surface 15a in the cross track
direction. The protrusion 19 has rail-state shape extending in the
cross track direction. The thickness (dimension in the x direction)
of the protrusion 19 is approximately 50 nm in one example, but it
is not limited to this. The protrusion 19 protrudes toward the
magnetic recording medium 14 by 0.5 to 2 .mu.m more than the
generator front end surface 16a when the thermal assisted magnetic
recording head is operated (in the figure, see the protrusion
length P).
[0045] It is advantageous to provide the protrusion 19 for the
following reasons. Asperities exist on the magnetic recording
medium 14 with a certain probability, and the convex part collides
with the air bearing surface S of the magnetic head slider 2 with a
certain probability. FIGS. 4A and 4B schematically show the state
in which the convex part 51 on the rotating magnetic recording
medium 14 approaches and collides with the magnetic head. The
protrusion 19 is not provided at the front end of the core 15. The
plasmon generator 16 protrudes more toward the magnetic recording
medium 14 than the core 15. This is because the plasmon generator
16 itself produces heat and causes thermal expansion due to thermal
energy of the propagating light 40 of the core 15, and protrudes
toward the magnetic recording medium 14 (FIG. 4A).
[0046] When the convex part 51 is within a certain range of height,
the convex part 51 approaches the plasmon generator 16 without
colliding with the core 15. Consequently, the convex part 51
directly collides against the plasmon generator 16 (FIG. 4B). At
this time, great stress and high temperature are instantaneously
generated, and the plasmon generator 16 is deformed. This
deformation causes the agglomeration on the generator front end
surface 16a of the plasmon generator 16. Even when the convex part
51 does not collide with the plasmon generator 16 but collides with
the main pole 10, the 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 to when the convex part 51
directly collides against the plasmon generator 16. Therefore, it
is also desirable to avoid mechanical collision between the main
pole 10 and the convex part 51, and it is desirable that the
protrusion 19 protrudes more toward the magnetic recording medium
14 than the main pole end surface 10a when the thermal assisted
magnetic recording head is operated.
[0047] With reference to FIGS. 5A to 5C, the protrusion 19
protrudes more than the main pole 10 and the plasmon generator 16.
The convex part 51 collides with the protrusion 19 and is deformed
on that occasion, and the height is reduced. In other words, the
protrusion 19 becomes a sacrificial part and collides with the
convex part 51, and the magnetic recording medium 14 is
substantially planarized (FIG. 5B). Then, as the convex part 51
approaches the plasmon generator 16, it passes through the magnetic
head without colliding with the plasmon generator 16 and the main
pole 10 (FIG. 5C). Because the protrusion 19 collides with the
convex part 51 first, direct physical contact between the convex
part 51 and the plasmon generator 16 is avoided. Thus, it becomes
difficult to generate agglomeration on the generator front end
surface 16a of the plasmon generator 16, enhancing thermal
reliability of the plasmon generator 16. Consequently, the
protrusion 19 protects the plasmon generator 16, and fulfills the
role of a so-called bumper.
[0048] It is believed that contamination that is adhered to the
magnetic recording medium 14 also functions similarly to the
asperity on the magnetic recording medium 14. Therefore, an effect
of contamination can also be reduced by providing the protrusion
19.
[0049] If the protrusion 19 is too close to the plasmon generator
16, the impact that the protrusion 19 receives is easily
transmitted to the plasmon generator 16, and the protrusion 19
cannot fulfill the role as a bumper. The space between the plasmon
generator 16 and the core 15 is filled with an insulator 18, such
as Al.sub.2O.sub.3, functioning also as the cladding 18, and the
interval is merely approximately 0.03 .mu.m. Therefore, it is not
preferable to provide the protrusion 19 between the plasmon
generator 16 and the core 15, and it is desirable that the
protrusion 19 be separated by a distance of not less than the
interval D between the plasmon generator 16 and the core 15, from
the generator front end surface 16a in the down track direction. In
the meantime, if the protrusion 19 is separated too far from the
plasmon generator 16, the protrusion 19 becomes closer to the MR
element 4. The MR element 4 is recessed by approximately 2 .mu.m
compared to the plasmon generator 16 when the thermal assisted
magnetic head is operated, and if the protrusion 19 is provided in
this vicinity, the protrusion 19 can no longer fulfill the role as
a bumper. From this viewpoint, it is not preferable that the
protrusion 19 be situated at a position exceeding 3 .mu.m from the
generator front end surface 16a in the down track direction. In
light of this, it is desirable that the protrusion 19 be situated
at a position of 0.03 to 3 .mu.m from the generator front end
surface 16a in the down track direction. In the present embodiment,
since the protrusion 19 passes on the surface 15a of the core 15
opposite to the magnetic recording medium 14, it is positioned
comparatively closer to the plasmon generator 16; however, as long
as the conditions above are fulfilled, the position of the
protrusion 19 is not limited.
[0050] The protrusion 19 preferably has a Mohs hardness of 5 or
more. The Mohs hardness herein means conventional Mohs hardness (10
levels), and does not mean new Mohs hardness (15 levels). The Mohs
hardness of the protrusion 19 is higher than Ni (Mohs hardness:
approximately 4) and Fe (Mohs hardness: approximately 4), which are
main materials of the leading shield 11. Since the leading shield
11 has a comparatively smaller Mohs hardness, peeling easily occurs
by repetition of the collision with the convex part 51 of the
magnetic recording medium 14. Such peeled pieces of the leading
shield 11 are captured between the protrusion 19 positioned at the
trailing side and the magnetic recording medium 14, and scrape the
surface of the protrusion 19. If the Mohs hardness of a peeled
piece is higher than that of the protrusion 19, the protrusion 19
becomes scratched and worn, gradually impairing its function as a
bumper. In the meantime, if the Mohs hardness of the protrusion 19
is higher than that of a peeled piece, it is difficult for the
protrusion 19 to become worn, and its function as a bumper can be
maintained for a long term. The protrusion 19 can be formed from
diamond, diamond-like carbon, boron nitride, titanium, vanadium,
chrome, zinc, neodymium, molybdenum, hafnium, tantalum, tungsten,
or an oxide or nitride of these.
[0051] The protrusion 19 preferably has a length 19w of 15 .mu.m or
longer in the cross track direction. If the length 19w in the cross
track direction is short, the wear of the protrusion 19 occurs
sooner, and it is difficult to maintain the function as a bumper
for a long term. Further, if the length 19w of the protrusion 19 is
15 .mu.m or longer, it is also effective in a touchdown process to
determine a reference point for determination of clearance between
the head and the magnetic recording medium 14. 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 the
present embodiment, the collision is detected when the magnetic
head makes contact with the protrusion 19. The protrusion 19, which
is long in the cross track direction, has a greater area for making
contact with the magnetic recording medium 14 than the main pole 10
and the plasmon generator 16, and easily detects the signal in
association with the contact.
[0052] Further, the length 19w of the protrusion 19 is preferably
100 .mu.m or less in the cross track direction. As described later,
an arm 230 where the thermal assisted magnetic head is attached
turns around a shaft 234 attached in a bearing part 233.
Consequently, depending upon where the thermal assisted magnetic
head is positioned in the radial direction on the magnetic
recording medium 14 (inner periphery side or outer periphery side),
a skew angle between the track circumferential direction of the
magnetic recording medium 14 and the down track direction of the
thermal assisted magnetic head is changed. In other words, the
direction when the convex part 51 on the magnetic recording medium
14 approaches the protrusion 19 is changed. In order to absorb the
change of the approaching direction of the convex part 51, a
protrusion 19 that is longer in the cross track direction is
advantageous. The length 19w is preferably at least 15 .mu.m, and
100 .mu.m at most is sufficient.
[0053] The thermal assisted magnetic recording head of the present
embodiment can be formed through the following steps: [0054] (1) On
a wafer (substrate 3), the lower part 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. [0055] (2) The
magnetic shield layer 8 is formed by the plating method. [0056] (3)
The leading shield 11 is formed by the plating method. [0057] (4)
The waveguide 17 made of a three-layer structure of cladding
18/core 15/cladding 18 is formed by sputtering. On this occasion,
by removing the end surface of the core 15 on the air bearing
surface S side, the protrusion 19 is formed. [0058] (5) The plasmon
generator 16 is formed by sputtering. [0059] (6) The main pole 10
is formed by the plating method. [0060] (7) The overcoat layer 25
is formed by sputtering. [0061] (8) The air bearing surface S is
formed by cutting the wafer into row bars, and by polishing and
milling the cut surfaces. [0062] (9) By cutting the row bars,
individual magnetic head sliders 2 are created. [0063] (10) By
positioning the laser diode unit 31 to the core 15 so as to couple
laser light with the core 15, the laser diode unit 31 is adhered to
the magnetic head slider 2.
[0064] In steps (1) to (7), a plurality of magnetic head sliders 2
are formed on the wafer in a lattice pattern. When step (7) is
finished, each magnetic head slider has the core 15, the plasmon
generator 16, the main pole 10 and the protrusion 19. In step (8),
the wafer is cut so as to allow the surface facing the generator
front end surface 16a to be a cut plane surface, and is divided
into row bars including the plurality of magnetic head sliders 2.
The row bar is an aggregate where the magnetic head sliders 2 are
arranged in a row or a plurality of rows. After that, the cut plane
surface of the row bar is pressed against a rotating polishing
board, and is polished. Polishing abrasive grains are embedded into
the polishing surface. The cut plane surface of the row bar is
further milled, and the air bearing surface S is formed. For the
milling, for example, ion milling can be used.
[0065] The protrusion 19 has a smaller polishing rate or a smaller
milling rate than other portions configuring the air bearing
surface S. Specifically, the protrusion 19 has a smaller polishing
rate or a smaller milling rate than the leading shield 11, the
insulator 18, such as Al.sub.2O.sub.3, between the leading shield
11 and the core 15, the main pole 10 and the like. Therefore, when
the protrusion 19 has a smaller polishing rate, on the occasion of
polishing in the step (8), the protrusion 19 will protrude more
than these other parts. Similarly, when the protrusion 19 has a
smaller milling rate, on the occasion of milling in step (8), the
protrusion 19 protrudes more than these other parts. Thus, the
protrusion 19 is formed according to (a) difference(s) in the
milling rate and/or the polishing rate. Polishing and milling are
performed on the row bars; however, these can be performed on
individual magnetic head sliders 2 after the row bars are further
divided into individual magnetic head sliders 2.
[0066] The protrusion 19 can be provided not at the core 15, but at
the leading shield 11. FIG. 6A is a similar figure to FIG. 3A
showing another embodiment of the present invention, and FIG. 6B is
a schematic view of main parts of the ABS viewed from the line 6-6
of FIG. 6A. The leading shield 11 has a chamfer 20 facing the
plasmon generator 16 and the magnetic recording medium 14, and a
protrusion 19a is provided at the chamfer 20. The chamfer 20 can be
formed, for example, by ion milling after the leading shield 11 is
created. An apex of the leading shield 11 is removed to be a
curved-state by milling, and the protrusion 19a is formed at the
removed portion, for example, by sputtering. This step can be
performed between steps (3) and (4). After the polishing and
milling in step (8) are performed, the protrusion 19a protrudes
from the shield end surface 11a of the leading shield 11 toward the
magnetic recording medium 14.
[0067] FIG. 7A is a similar figure to FIG. 3A further showing
another embodiment of the present invention, and FIG. 7B is a
schematic view of main parts of the ABS viewed from the line 7-7 of
FIG. 7A. In the present embodiment, after the air bearing surface S
of the magnetic head slider is formed, a protrusion 19b can be
formed on the shield end surface 11a of the leading shield 11. The
protrusion 19 can be formed by sputtering between steps (8) and (9)
or between steps (9) and (10). The entire protrusion 19b formed as
mentioned above protrudes from the shield end surface 11a of the
leading shield 11 toward the magnetic recording medium 14. The
present embodiment is characterized by formation of the protrusion
19b on the polished and milled cut plane surface, and the
protrusion 19b can also be provided on the end surface 15a of the
core 15.
[0068] Next, a head gimbal assembly (HGA) where the thermal
assisted magnetic recording head is mounted is explained.
[0069] With reference to FIG. 8, 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 222 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 thermal assisted magnetic
recording head 1 is attached.
[0070] 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 intermediate 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.
[0071] Next, with reference to FIG. 9 and FIG. 10, 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 arms. FIG. 9 is a side
view of the head stack assembly, and FIG. 10 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.
[0072] With reference to FIG. 10, 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. In every
magnetic recording medium 14, two thermal assisted magnetic
recording heads 1 are arranged to be opposite 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.
[0073] Although the desired embodiments of the present invention
were presented and explained in detail, readers should understand
that various modifications and amendments are possible as long as
they do not depart from the effect or the scope of attached
claims.
* * * * *