U.S. patent application number 16/953925 was filed with the patent office on 2022-05-26 for writer with adaptive side gap.
The applicant listed for this patent is Headway Technologies, Inc.. Invention is credited to Jiun-Ting Lee, Xiaomin Liu, Ying Liu, Yue Liu, Yuhui Tang, Shengyuan Wang.
Application Number | 20220165300 16/953925 |
Document ID | / |
Family ID | |
Filed Date | 2022-05-26 |
United States Patent
Application |
20220165300 |
Kind Code |
A1 |
Liu; Ying ; et al. |
May 26, 2022 |
WRITER WITH ADAPTIVE SIDE GAP
Abstract
A PMR (perpendicular magnetic recording) write head configured
for thermally assisted magnetic recording (TAMR) and microwave
assisted magnetic recording (MAMR) is made adaptive to writing at
different frequencies by inserting thin layers of magnetic material
into the material filling the side gaps (SG) between the magnetic
pole (MP) and the side shields (SS). At high frequencies, the thin
magnetic layers saturate and lower the magnetic potential of the
bulky side shields
Inventors: |
Liu; Ying; (San Jose,
CA) ; Tang; Yuhui; (Milpitas, CA) ; Liu;
Yue; (Fremont, CA) ; Lee; Jiun-Ting;
(Sunnyvale, CA) ; Wang; Shengyuan; (San Jose,
CA) ; Liu; Xiaomin; (Fremont, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Headway Technologies, Inc. |
Milpitas |
CA |
US |
|
|
Appl. No.: |
16/953925 |
Filed: |
November 20, 2020 |
International
Class: |
G11B 5/31 20060101
G11B005/31; G11B 5/23 20060101 G11B005/23; G11B 5/48 20060101
G11B005/48 |
Claims
1. A perpendicular magnetic recording (PMR) writer with adaptive
gap structure comprising: a main magnetic pole (MP) having a
trapezoidal, planar, air-bearing surface (ABS) face symmetrically
positioned relative to surrounding magnetic shields; wherein said
trapezoidal face has a narrow leading edge, a trailing edge that is
wider than said leading edge and sloping sides connecting said
trailing and leading edges; wherein, in said ABS cross-sectional
plane, said MP face is separated from inner edges of said
surrounding magnetic shields by a connected series of
material-filled gaps comprising: a write gap (WG) separating said
MP trailing edge from an inner edge of a trailing shield, said WG
having a lateral width exceeding said MP trailing edge width; a
leading edge gap (LG) separating said MP leading edge from an inner
edge of a leading shield (LS) and a pair of mirror-symmetrically
placed side gaps (SG) separating said sloping MP sides from said
side shields (SS); wherein said two SG intersect said WG and said
LG symmetrically, forming a continuous layer completely surrounding
said trapezoidal face of said MP; wherein said WG is filled
uniformly with non-magnetic, non-conducting material; wherein said
two SG and said LG are filled with non-magnetic, non-conducting
material in which are completely embedded N sequentially formed and
nested thin layers of magnetic material that are completely
surrounded by layers of said non-magnetic, non-conducting material,
wherein each of said N thin layers of magnetic material is formed
as three continuously connected linear edges that partially
surround and are parallel to edges of said MP trapezoidal face with
the exception of said WG trailing edge; whereby said three
connected linear edges of each of said N thin layers of magnetic
material are parallel to respective adjacent ones of said sloping
sides and said leading edge of said MP trapezoidal face, and are
parallel to but separated from inner edges of said SS and LS by
layers of non-magnetic, non-conducting material and do not touch
adjacent magnetic layers where such layers exist, and terminate at,
but do not extend into said WG non-magnetic, non-conducting
material, whereby if N is greater than 1, said N thin layers of
magnetic material are nested symmetrically within each other and
are open at said WG; wherein said gap structure is adaptable to
various writing frequencies as said structure comprising N thin,
embedded, nested layers has higher permeability at low frequencies
and lower permeability at high frequencies and writability of said
PMR is enhanced by said variability.
2. The perpendicular magnetic recording (PMR) writer of claim 1
wherein N=1 and there is one said completely embedded layer of
magnetic material and it does not touch either the MP or the
surrounding shield material.
3. The perpendicular magnetic recording (PMR) writer of claim 1
wherein N=2 and there are two said completely embedded layers of
magnetic material that are nested symmetrically within each other
and wherein neither embedded layer touches the other or the
magnetic material of the MP or said shields.
4. The perpendicular magnetic recording (PMR) writer of claim 1
wherein the thickness of each completely embedded magnetic layer is
between 1 nm and 50 nm.
5. The perpendicular magnetic recording (PMR) writer of claim 2
wherein the single magnetic layer is separated from the shields and
the MP by a non-magnetic, non-conducting layer of thickness between
1 nm and 50 nm adjacent to each side of said magnetic layer.
6. A perpendicular magnetic recording (PMR) writer configured for
TAMR operation and having an adaptive gap structure, comprising:
the perpendicular magnetic recording (PMR) writer with adaptive gap
structure of claim 1 a source of optical radiation; a waveguide
configured to carry said optical radiation to said ABS a near-field
transducer configured to couple to said waveguide and generate
near-field energy at a recording spot on a magnetic recording
medium said PMR of claim 1, providing a magnetic flux for recording
at said spot.
7. A perpendicular magnetic recording (PMR) writer configured for
MAMR operation and having an adaptable gap structure, comprising:
the perpendicular magnetic recording (PMR) writer with adaptive gap
structure of claim 1 a source of microwave radiation; a transducer
configured to couple to said microwave radiation and generate
microwave energy in the form of resonant precessional motion of
magnetic recording bits at a recording spot on a magnetic recording
medium; said PMR of claim 1, providing a magnetic flux for
recording at said spot.
8. A perpendicular magnetic recording (PMR) writer configured for
MAMR operation and having an adaptable gap structure, comprising:
the perpendicular magnetic recording (PMR) writer with adaptive gap
structure of claim 1 a source of microwave radiation; a transducer
configured to couple to said microwave radiation and generate
microwave energy at a recording spot on a magnetic recording
medium; the PMR of claim 1 further configured for spin-assisted
writing wherein a spin-torque layer formed within a write gap,
assists a flux guiding layer (FGL), also within said write gap, to
flip a magnetization in an opposite direction to a write-gap
magnetic field, thereby strengthening the magnetic field emerging
from the ABS surface of the MP and returning through the trailing
shield, thereby providing an enhanced magnetic flux for recording
at said spot. said PMR of claim 1 providing said enhanced magnetic
flux.
9. A head-gimbal assembly, comprising: the TAMR-configured
read/write head of claim 6 a suspension that elastically supports
said TAMR-configured read/write head, a flexure affixed to said
suspension and a load beam having one end attached to said flexure
and another end attached to a base plate.
10. A HDD (Hard Disk Drive), comprising: the head gimbal assembly
of claim 9 a magnetic recording medium positioned opposite to said
slider-mounted PMR; a spindle motor that rotates and drives said
magnetic recording medium; a device that supports the slider and
that positions said slider relative to said magnetic recording
medium.
11. A head-gimbal assembly, comprising: the MAMR-configured
read/write head of claim 8 a suspension that elastically supports
said TAMR-configured read/write head, a flexure affixed to said
suspension and a load beam having one end attached to said flexure
and another end attached to a base plate.
12. A HDD (Hard Disk Drive), comprising: the head gimbal assembly
of claim 11 a magnetic recording medium positioned opposite to said
slider-mounted PMR; a spindle motor that rotates and drives said
magnetic recording medium; a device that supports the slider and
that positions said slider relative to said magnetic recording
medium.
13. A head-gimbal assembly, comprising: the MAMR-configured
read/write head of claim 7 a suspension that elastically supports
said TAMR-configured read/write head, a flexure affixed to said
suspension and a load beam having one end attached to said flexure
and another end attached to a base plate.
14. A HDD (Hard Disk Drive), comprising: the head gimbal assembly
of claim 13 a magnetic recording medium positioned opposite to said
slider-mounted PMR; a spindle motor that rotates and drives said
magnetic recording medium; a device that supports the slider and
that positions said slider relative to said magnetic recording
medium.
Description
RELATED PATENT APPLICATIONS
[0001] This application is related to U.S. Pat. Nos. 10,522,174,
10,490,216, and 10,424,326 all of which are assigned to a common
assignee and fully incorporated by reference.
BACKGROUND
1. Technical Field
[0002] This disclosure relates generally to a thin-film magnetic
writer and particularly to the structure of the gaps surrounding
the main pole (MP).
[0003] 2. Background
[0004] As Hard Disk Drive (HDD) requires higher and higher areal
density capability. Both tracks per inch (TPI) and bits per inch
(BPI) need to be larger. Because higher TPI requires smaller Main
Pole (MP) size, the writability under high frequency writing will
be a major challenge for next generation HDD writer head.
[0005] In the current writer design, the MP is surrounded by a
trailing shield (TS), a side shield (SS) and a leading shield (LS)
and separated from them by gaps, typically filled with a wide range
of non-magnetic materials. It is critical to optimize the gap width
between the MP and these surrounding shields. Smaller gap width
will enhance a shielding effect and sharpen the written bit
pattern, while larger gap width can help release MP flux and
promote writability. Because low frequency writing benefits more
from written pattern sharpness whereas high frequency writing is
hungry for writability (i.e., strength of MP field), a gap width
that can adapt writing frequency is strongly desired.
SUMMARY
[0006] In this disclosure we propose a new design for the gap
structure that separates the main pole (MP) from its surrounding
shields. Specifically, we deposit thin layers of non-magnetic
material and magnetic material sequentially on top of a normal side
shield (SS) and/or leading shield (LS). Because the thin magnetic
layers are decoupled from the bulky shielding material, the thin
magnetic layers can help absorb the gap field and reduce bulky
shield magnetic potential, while protecting against write bubble
fringing and reducing erase width of an AC field (EWAC).
[0007] The thin magnetic layers can have a different frequency
response than the bulky shields. In low frequency writing, the thin
layers will have higher permeability and provide normal shielding.
Under high frequency conditions, however, the thin layers will have
lower permeability and the effective gap size will become larger.
As a result, the gap structure is adaptable to varying recording
conditions, MP flux release is improved and writability is
enhanced.
[0008] Finally, the improved performance of the PMR writer makes it
particularly well designed to operate in conjunction with thermally
assisted magnetic recording (TAMR) and microwave assisted magnetic
recording (MAMR). As is now well known in the art and so will not
be further described herein, TAMR reduces the coercivity of a
region of a recording medium on which recording is to occur by
raising its temperature, typically using the optical field energy
of a laser to create plasmons whose near-fields are not diffraction
limited and, therefore, can be finely focused on the recording spot
of the magnetic medium.
[0009] One form of MAMR achieves an analogous result as TAMR, but
with a different mechanism. This form, called a spin-torque
oscillator (STO), typically operates by applying a microwave
frequency field to the recording media, creating a resonant
precessional motion in the magnetic bits. This excess energy allows
the bits to make magnetic transitions more readily, effectively
reducing the coercivity of the magnetic medium.
[0010] The second form of MAMR, which we will call spin-assisted
writing (SAW), effectively enhances the write-field impinging
directly on the media surface from the pole tip by enhancing the
flux between the magnetic pole tip and the trailing shield. This
enhancement of the field leaving the pole tip is produced by
generating a counter-field to the field within the write-gap by
using a spin-torque layer in combination with a flux guiding layer
to produce a field that is counter to the field generated by the
pole. Thus, instead of giving more energy to the magnetic bits by
the RF precessional field, it enhances the write field that
impinges upon them by eliminating the field within the write gap.
Both of these recording assist technologies will be well suited to
operating along with the improved writability of the presently
disclosed PMR with an adaptable gap design.
[0011] Referring to FIG. 1C, there is shown a schematic side
cross-sectional view of the distal end of the PMR write head. The
write pole is 10, the trailing shield is 150, a spin polarization
layer is 170, a flux control layer is 160. In this figure the flux
control layer creates a magnetic field 190 that is opposite to the
gap field 180 and reduces it. As a result, the field emanating from
the pole 10 is strengthened and can cause bit reversals without the
need for RF oscillations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1A is a schematic illustration of the ABS of a prior
art write head showing a write gap (WG) and side gaps (SG).
[0013] FIG. 1B is a schematic illustration of the ABS view of the
presently disclosed write head, showing the layered construction of
the side gaps.
[0014] FIG. 1C is a schematic illustration of main pole tip (MP), a
trailing shield and a spin polarization layer and flux control
layer as they would be configured for spin-assisted writing.
[0015] FIG. 2A is a schematic illustration of the ABS of the prior
art write head of FIG. 1A showing the SG with a width of 35 nm for
the purposes of a simulation.
[0016] FIG. 2B is a schematic illustration of the ABS of the
presently disclosed write head, showing SG1 with a width of 35 nm
and SG2 with a width of 60 nm, for the purposes of the
simulation.
[0017] FIG. 2C is a schematic illustration of the ABS of the prior
art write head of FIG. 1A showing the SG with a width of 60 nm for
the purposes of the simulation.
[0018] FIG. 3A is a graphical plot of the simulated downtrack Hy,
measured in Oersteds (Oe), of 4 different head designs.
[0019] FIG. 3B is a graphical plot of the simulated crosstrack Hy
plot of the 4 different head designs of FIG. 3A.
[0020] FIG. 4A shows dynamic adjacent track erasure (ATE) mapping
from the modeling result for a prior art design.
[0021] FIG. 4B shows dynamic adjacent track erasure (ATE) mapping
from the modeling result for the presently disclosed layered
design.
[0022] FIG. 5 schematically shows a perspective view of a head arm
assembly of the present recording apparatus.
[0023] FIG. 6 schematically shows a side view of a head stack
assembly of the present recording apparatus.
[0024] FIG. 7 schematically shows a plan view of the magnetic
recording apparatus within which are mounted the components shown
if FIGS. 5 and 6.
DETAILED DESCRIPTION
[0025] Referring to FIG. 1A there is shown a prior art write head
in an ABS view. The trapezoidal cross-section of the MP tip 10 is
separated from magnetic shield material 100 by a series of
surrounding gaps that are here filled with dielectric
(non-magnetic) material. The gaps are formed by separations between
the inner edges of the side shields (SS), the trailing shield (TS)
and the leading shield (LS) and outer edges of the trapezoidal
cross-sectional shape of the MP.
[0026] A write gap (WG) 20 covers the trailing edge of the MP 10
and extends laterally and symmetrically over the trailing edge and
terminates beyond the width of the trailing edge. Magnetic shield
material 30 of the trailing shield (TS) covers the WG 20. The
downward sloping sides of the MP are each covered by side gaps (SG)
40 that are connected by a leading gap (LG) 50. The side gaps
contact the material of the side shields 100 (SS) and the leading
gap (LG) 50 contacts the leading shield (LS) material 70. During
operation, the flux lines of the magnetic recording field emanate
from the trapezoidal tip of the MP 10, strike the recording medium
(not shown) and return to the surrounding shields to complete the
flux path.
[0027] Referring to schematic FIG. 1B, there is shown the structure
provided by the present disclosure. In the structure of FIG. 1B
there is shown that three layers of dielectric (non-magnetic)
material 42, 44 and 46 and two layers of magnetic material 62 and
64 are deposited sequentially in the side gaps (SG) and leading gap
(LG). The structure can include a single thin magnetic layer
surrounded by dielectric material (not shown), or it can include
several nested magnetic layers as shown in FIG. 1B. Note also that
the thin magnetic layers are separated from the MP and shields by a
layer of dielectric 42, 46 to decouple them from the bulkier
magnetic material of the MP and shields.
[0028] To demonstrate the performance of this presently disclosed
structure, several simulations using magnetic modeling were carried
out. Referring to FIG. 2A, there is shown a prior art structure
with a SG 40a of 35 nm (nanometers) width that is in all respects
identical to SG 40 in FIG. 1A except it is to be used in a finite
element analysis, so an SG width of 35 nm has been assigned to it.
We note that the thickness of each non-magnetic layer can vary from
1 nm to 50 nm and the thickness of each magnetic layer can vary
from 1 nm to 50 nm.
[0029] Referring to FIG. 2B there is shown the new structure in
which a single thin magnetic layer 62 of 20 nm thickness has been
formed inside the two side gaps SG and the leading gap LG. The
symbol SG1 is the gap between MP and the nearest magnetic layer and
SG2 denotes the width between the pole and side shield.
[0030] The magnetic layer 62 is separated from the MP 10 by
dielectric layer 46 having a width shown as SG1 and from side
shield 100 by dielectric layer 42. Separating the magnetic layer 62
from the shield 100 and pole 10 is required in order to decouple
the magnetic layer from the bulkier magnetic shields and pole.
[0031] FIG. 2C shows the same prior art structure as FIG. 2A,
except that the thickness of the gap 40a in FIG. 2A is taken to be
35 nm for the purpose of a simulation, while the thickness of the
gap 40b in prior art FIG. 2C is taken to be 60 nm for the purpose
of a simulation.
[0032] Referring to FIG. 3A, there are shown simulated profiles
(under static conditions) of the down-track (in .mu.m) strength of
Hy (in Oersteds) for four different simulated structures, two prior
art heads with no embedded thin magnetic layer and with the
dielectric thicknesses being 35 nm and 40 nm and with two of the
new designs, in which the SG thickness is 35 nm and the embedded
thin magnetic layer has a total Ms of 12 kG or 4 kG
(kilogauss).
[0033] The profiles shown in FIG. 3B are for the same four heads,
but now simulating their cross-track (in .mu.m) values of Hy.
Looking at the two sets of profiles, it can be seen that the new
designs (with embedded layers) enhance the maximum Hy peak height,
while EWAC confinement (profile width) is as good as is obtained
with the prior art designs (no embedded layers). The results also
demonstrate that the thin magnetic layer saturates and helps to
lower the magnetic potential of the bulky side shield. As a result,
for all frequency domains, writability can be gained without the
loss of write bubble fringing and also improving skip track
erasure.
[0034] Referring to FIGS. 4A and 4B there is shown the use of
dynamic modeling to show the adjacent track erasure (ATE) produced
by the prior art head (FIG. 4A) and the head of the present design
(FIG. 4B). The writing frequency used in this simulation is 1.5
GHz. In both head designs only the left side of the side shield
shows any stray field leakage, indicating that the stray field
comes mainly from domain rotation during the write transitions.
[0035] The new design (FIG. 4B) shows a cleaner stray field than
the prior art design (FIG. 4A). The protection of the bulky side
shield by the thin magnetic layer is proved by this modeling. It is
to be noted that the dynamic modeling result just performed does
not include the dynamic permeability effects in NiFe thin films.
However, it has been reported (O. Acher, S. Queste and M. Ledieu,
Physical Review B 68, 184414 (2003)) that the permeability of the
NiFe thin film drops dramatically under a higher frequency external
field. The dynamic behavior will be further influenced by this
property. In a new structure like that in FIG. 2B, low frequency
writing will behave more like FIG. 2A and high frequency writing
will behave more like FIG. 2C. Thus, the effective side gap is
indeed adaptive to the writing frequency. Although our simulations
have been carried out based on PMR (perpendicular magnetic
recording) writing, the design is equally appropriate for use in
MAMR and TAMR configurations and other magnetic recording
heads.
[0036] Referring now to FIGS. 5, 6 and 7, there is shown the
elements of a magnetic recording apparatus, such as a MAMR
configured hard disk drive (HDD), through whose use the PMR writer
described above will meet remaining objects of this disclosure.
[0037] FIG. 5 shows a head gimbal assembly (HGA) 1200 that includes
a slider-mounted PMR writer 1100, the slider now providing
aerodynamic support to the writer when it moves above or below an
operational disk recording medium 1140. There is also shown a
suspension 1220 that elastically supports the slider-mounted writer
1100. The suspension 1220 has a spring-like load beam 1230 made
with a thin, corrosion-free elastic material like stainless steel.
A flexure 1230 is provided at a distal end of the load beam and a
base-plate 1240 is provided at the proximal end. The slider mounted
TAMR writer 1100 is attached to the load beam 1230 at the flexure
1231 which provides the TAMR with the proper amount of freedom of
motion. A gimbal part for maintaining the PMR read/write head at a
proper level is provided in a portion of the flexure 1231 to which
the TAMR 1100 is mounted.
[0038] A member to which the HGA 1200 is mounted to arm 1260 is
referred to as head arm assembly 1220. The arm 1260 moves the
read/write head 1100 in the cross-track direction (arrow) across
the medium 1140 (here, a hard disk). One end of the arm 1260 is
mounted to the base plate 1240. A coil 1231 to be a part of a voice
coil motor (not shown) is mounted to the other end of the arm 1260.
A bearing part 1233 is provided to the intermediate portion of the
arm 1260. The arm 1260 is rotatably supported by a shaft 1234
mounted to the bearing part 1233. The arm 1260 and the voice coil
motor that drives the arm 1260 configure an actuator.
[0039] Referring next to FIG. 6 and FIG. 7, there is shown a head
stack assembly 1250 and a magnetic recording apparatus in which the
slider-mounted TAMR writer 1100 is contained. The head stack
assembly is an element to which the HGA 1200 is mounted to arms of
a carriage having a plurality of arms for engaging with a plurality
of disks 1140. The plurality of disks are mounted on a spindle
1261. FIG. 5 is a side view of this assembly and FIG. 6 is a plan
view of the entire magnetic recording apparatus.
[0040] Referring finally to FIG. 7, the head stack assembly 1250 is
shown incorporated into a magnetic recording apparatus 1290. The
magnetic recording apparatus 1290 has a plurality of magnetic
recording media 1114 mounted on a spindle motor 1261. Each
individual recording media 1114 has two TAMR elements 1100 arranged
opposite to each other across the magnetic recording media 14
(shown clearly in FIG. 5). The head stack assembly 1250 and the
actuator (except for the write head itself) act as a positioning
device and support the PMR heads 1100. They also position the PMR
heads correctly opposite the media surface in response to
electronic signals. The read/write head records information onto
the surface of the magnetic media by means of the magnetic pole
contained therein.
[0041] As is finally understood by a person skilled in the art, the
detailed description given above is illustrative of the present
disclosure rather than limiting of the present disclosure.
Revisions and modifications may be made to methods, materials,
structures and dimensions employed in forming and providing a PMR
writer configured for TAMR or MAMR operation having an adaptive gap
structure produced by magnetic thin film laminations within
dielectric, non-magnetic gap material, while still forming and
providing such a structure and its method of formation in accord
with the spirit and scope of the present invention as defined by
the appended claims.
* * * * *