U.S. patent application number 16/506222 was filed with the patent office on 2019-12-12 for microwave assisted magnetic recording drive utilizing interlaced track recording.
The applicant listed for this patent is Seagate Technology LLC. Invention is credited to Mehmet Fatih Erden, Steven Douglas Granz.
Application Number | 20190378541 16/506222 |
Document ID | / |
Family ID | 67106362 |
Filed Date | 2019-12-12 |
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United States Patent
Application |
20190378541 |
Kind Code |
A1 |
Granz; Steven Douglas ; et
al. |
December 12, 2019 |
MICROWAVE ASSISTED MAGNETIC RECORDING DRIVE UTILIZING INTERLACED
TRACK RECORDING
Abstract
Bottom tracks are written to a recording medium using a first
setting of a spin-torque oscillator of a single microwave assisted
magnetic recording (MAMR) head. Top tracks are written interlaced
between and partially overlapping the bottom tracks using the
single MAMR head at a second setting of the MAMR head, the first
and second settings resulting in different bit aspect ratios for
the top and bottom tracks.
Inventors: |
Granz; Steven Douglas;
(Shakopee, MN) ; Erden; Mehmet Fatih; (St. Louis
Park, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Seagate Technology LLC |
Cupertino |
CA |
US |
|
|
Family ID: |
67106362 |
Appl. No.: |
16/506222 |
Filed: |
July 9, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
16006345 |
Jun 12, 2018 |
10347285 |
|
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16506222 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11B 20/1217 20130101;
G11B 2020/1292 20130101; G11B 5/012 20130101; G11B 2005/0024
20130101; G11B 2020/1238 20130101 |
International
Class: |
G11B 20/12 20060101
G11B020/12 |
Claims
1-20. (canceled)
21. A method, comprising: writing bottom tracks to a recording
medium using a first setting of a spin-torque oscillator of a
single microwave assisted magnetic recording (MAMR) head; writing
top tracks interlaced between and partially overlapping the bottom
tracks using the single MAMR head at a second setting of the
spin-torque oscillator, the first and second settings resulting in
different bit aspect ratios for the top and bottom tracks.
22. The method of claim 21, wherein the first and second settings
comprise first and second microwave powers of the spin-torque
oscillator.
23. The method of claim 21, wherein for one of the first and second
settings, no power is applied to the spin-torque oscillator--and
for another of the first and second settings a non-zero power is
applied to the spin-torque oscillator.
24. The method of claim 21, wherein the first and second settings
comprise first and second different combinations of spin-torque
oscillator power and spin-torque oscillator frequency.
25. The method of claim 21, wherein the bottom and top tracks are
written at different track widths.
26. The method of claim 21, wherein the bottom and top tracks are
written at different linear bit densities.
27. The method of claim 21, wherein the bottom tracks are assigned
to a first logical group and the top tracks are assigned to a
second logical band, tracks within the first and second logical
bands being treated as adjacent tracks during reading and
writing.
28. The method of claim 21, further comprising, before writing the
top and bottom tracks, performing a procedure to determine a target
linear bit density of the bottom tracks, the procedure comprising:
writing first bottom test tracks at increasing linear bit densities
until a maximum allowable bit error rate is measured; determining a
maximum linear bit density associated with the maximum allowable
bit error rate; starting with the maximum linear bit density,
writing second bottom test tracks at decreasing linear bit
densities until a threshold bit error rate is determined; and
setting the target linear bit density of the bottom tracks based on
a linear bit density corresponding to the threshold bit error
rate.
29. The method of claim 28, wherein the procedure further
comprises: writing top test tracks at increasing linear bit
densities until a second maximum bit error rate is measured at a
target linear bit density of the top tracks; if writing the top
tracks at the target linear bit density partially overlapping the
bottom tracks does not increase the threshold bit error rate of the
bottom tracks beyond a threshold, using the target linear bit
density of the top tracks to write the top tracks, otherwise using
a reduced linear bit density less than for one of the top and
bottom tracks.
30. An apparatus, comprising: interface circuitry operable to
control a spin-torque oscillator of a single microwave assisted
magnetic recording (MAMR) head; and a controller coupled to the
interface circuitry, the controller configured to: write bottom
tracks to a recording medium of the apparatus using the single MAMR
head at a first setting of the spin-torque oscillator; write top
tracks interlaced between and partially overlapping the bottom
tracks using the single MAMR head at a second setting of the
spin-torque oscillator, the first and second settings resulting in
different bit aspect ratios for the top and bottom tracks.
31. The apparatus of claim 30, wherein the first and second
settings comprise first and second microwave powers of the
spin-torque oscillator.
32. The apparatus of claim 30, wherein for one of the first and
second settings, no power is applied to the spin torque oscillator
and for another of the first and second settings a non-zero power
is applied to the spin-torque oscillator.
33. The apparatus of claim 30, wherein the first and second
settings comprise first and second different combinations of
spin-torque oscillator power and spin-torque oscillator
frequency.
34. The apparatus of claim 30, wherein the bottom and top tracks
are written at different track widths.
35. The apparatus of claim 30, wherein the bottom and top tracks
are written at different linear bit densities.
36. The apparatus of claim 30, wherein the bottom tracks are
assigned to a first logical group and the top tracks are assigned
to a second logical band, tracks within the first and second
logical bands being treated as adjacent tracks during reading and
writing.
37. A method, comprising: writing first bottom test tracks to a
recording medium at a first setting of a spin-torque oscillator of
a single microwave assisted magnetic recording (MAMR), linear bit
densities of the first bottom tracks increased until a maximum
allowable bit error rate is measured at a maximum linear bit
density; starting with the maximum linear bit density, writing
second bottom test tracks using the single MAMR head at the first
setting, linear bit densities of the second bottom test tracks
increased until a threshold bit error rate is determined
corresponding to an operational bottom track linear bit density;
writing top test tracks using the single MAMR head at a second
setting of the spin torque oscillator over third bottom test tracks
written at the operational bottom track linear bit density, linear
bit densities of the top test tracks increased until a second
maximum bit error rate is measured at an operational top track
linear bit density; and using the operational bottom and top linear
bit densities to record respective interleaved top and bottom
operational tracks using the single MAMR head.
38. The method of claim 37, further comprising, if writing the top
test tracks at the operational top track linear bit density over
the third bottom test tracks increases a bit error rate of the
bottom test tracks past the threshold bit error rate plus a delta,
reducing the operational bottom track linear bit density.
39. The method of claim 37, further comprising, if writing the top
test tracks at the operational top track linear bit density over
the third bottom test tracks increases a bit error rate of the
bottom test tracks past the threshold bit error rate plus a delta,
reducing the operational top track linear bit density.
40. The method of claim 37, further comprising, if writing the top
test tracks at the operational top track linear bit density over
the third bottom test tracks increases a bit error rate of the
bottom test tracks past the threshold bit error rate plus a delta,
decreasing a track width of the top operational tracks.
Description
RELATED PATENT DOCUMENTS
[0001] This application is a continuation of U.S. application Ser.
No. 16/006,345, filed Jun. 12, 2018, which is incorporated herein
by reference in its entirety
SUMMARY
[0002] Various embodiments described herein are generally directed
to a microwave assisted magnetic recording drive utilizing
interlaced track recording. In one embodiment, bottom tracks are
written to a recording medium using a first setting of a microwave
assisted magnetic recording (MAMR) head. Top tracks are interlaced
between and partially overlapping the bottom tracks using a second
setting of the MAMR head, the second setting resulting in a
narrower track width than the first setting.
[0003] In another embodiment, bottom tracks are written to a
recording medium using a first microwave power of a MAMR head and a
first linear bit density. The first microwave power results in a
first track width of the bottom tracks. Top tracks are written
interlaced between and partially overlapping the bottom tracks
using a second microwave power of the MAMR head and a second linear
bit density. The second microwave power is lower than the first
microwave power and results in a second track width less than the
first track width. These and other features and aspects of various
embodiments may be understood in view of the following detailed
discussion and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The discussion below makes reference to the following
figures, wherein the same reference number may be used to identify
the similar/same component in multiple figures.
[0005] FIG. 1 is a diagram illustrating a magnetic recording device
according to an example embodiment;
[0006] FIG. 2 is a diagram illustrating interlaced magnetic
recording tracks according to an example embodiment;
[0007] FIG. 3 is a block diagram illustrating interlaced and
shingled tracks according to an example embodiment;
[0008] FIG. 4 is a block diagram illustrating a recording schemed
according to an example embodiment;
[0009] FIGS. 5 and 6 are flowcharts illustrating a procedure
according to an example embodiment;
[0010] FIG. 7 is a block diagram of an apparatus according to an
example embodiment; and
[0011] FIG. 8 is a flowchart of a method according to an example
embodiment.
DETAILED DESCRIPTION
[0012] The present disclosure generally relates to data storage
devices that utilize magnetic storage media, e.g., disks. Recording
schemes have been developed to increase areal density for
conventional magnetic recording (CMR) devices, e.g., perpendicular
magnetic recording (PMR) as well as devices using newer
technologies, such as heat-assisted magnetic recording (HAMR),
microwave-assisted magnetic recording (MAMR). One of these
recording schemes is interlaced magnetic recording (IMR), which
generally involves writing some tracks that partially overlap
previously written tracks. This allows writing the tracks at a
narrower width than would be possible in conventional recording
schemes, where tracks are spaced apart to prevent crosstrack
interference. While IMR-recorded tracks cannot be randomly updated
as easily as conventionally-recorded tracks, the drive architecture
can be adapted to minimize the effects on random writes.
[0013] In a disk drive utilizing interleaved magnetic recording
(IMR), there are two types of data tracks written. The first is a
bottom track, which is generally written at higher linear density
using a wider write head, or using a write configuration that
results in a wider track being written. The second is a top track,
which is generally written at lower linear density using a narrower
write head, or using a write configuration that results in a wider
track being written. The bottom tracks are written first, with a
relatively wide spacing between, and then the top tracks are
written in the spacing between adjacent top tracks. The intent of
writing the top tracks is to encroach enough on the adjacent bottom
tracks to partially overwrite the bottom track edges. Because these
track edges tend to have poorer SNR than the middle of the track,
overwriting the edges has a minor impact on the overall bottom
track SNR.
[0014] The different characteristics of the top and bottom IMR
tracks can complicate writing the data from those tracks. The top
and bottom tracks will usually have different characteristics,
including track width, linear bit-density, signal-to-noise ratio,
etc. Typically, a conventional write pole will not significantly
increase write width (which defines track width) in response to
changes in write current applied to a write coil that magnetizes
the pole. Therefore, IMR recording that utilizes conventional
recording heads (e.g., PMR writer) may use strategies such as two
or more writers with different widths to write top and bottom
tracks.
[0015] In order to reduce costs and complexity, it is desirable to
have a single write transducer that can write both top and bottom
tracks in an IMR drive. In embodiments described below, a MAMR
write transducer is used to write tracks having different width and
other characteristics. Such a transducer can be used to write the
top and bottom tracks for IMR with a single head, and may have
other uses. For example, in some cases a drive may be configured to
write data with different bit-aspect ratios (BAR) in different
regions of the drive. This may be used to maximize storage space,
increase performance, customize performance for end-user
specification, etc. Being able to write at significantly different
track widths via MAMR allows a wider range of BAR to be used.
[0016] In FIG. 1, a block diagram shows a side view of a read/write
head 102 (also referred to as a "read head," "write head,"
"recording head," etc.) according to an example embodiment. The
read/write head 102 may also be referred to herein as a write head,
read head, recording head, etc. The read/write head 102 is part of
slider that is coupled to an arm 104 by way of a suspension 106,
e.g., a gimbal. The read/write head 102 includes read/write
transducers 108 at a trailing edge that are held proximate to a
surface 110 of a magnetic recording medium 111, e.g., a magnetic
disk. When the read/write head 102 is located over surface 110 of
recording medium 111, a flying height 112 is maintained between the
read/write head 102 and the surface 110 by a downward force of arm
104. This downward force is counterbalanced by an air cushion that
exists between the surface 110 and an air bearing surface (ABS) 103
(also referred to herein as a "media-facing surface") of the
read/write head 102 when the recording medium 111 is rotating.
[0017] In order to provide control of the clearance between the
read/write transducers 108 and the recording medium 111, one or
more clearance actuators 114 (e.g., heaters) are formed in the
read/write head 102. A current applied to the heater 114 induces a
local protrusion which varies the clearance. The amount of current
applied to the heater 114 may vary based on which of the read/write
transducers 108 are in use, and may also be adjusted to account for
irregularities in the media surface 110, changes in ambient
temperature, location of the read/write head 102 over the medium
111, etc.
[0018] A controller 118 is coupled to the read/write transducers
108, as well as other components of the read/write head 102, such
as heaters 114, sensors, etc. The controller 118 may be part of
general- or special-purpose logic circuitry that controls the
functions of a storage device that includes at least the read/write
head 102 and recording medium 111. The controller 118 may include
or be coupled to a read/write channel 119 that include circuits
such as preamplifiers, buffers, filters, digital-to-analog
converters, analog-to-digital converters, decoders, encoders, etc.,
that facilitate electrically coupling the logic of the controller
118 to the signals used by the read/write head 102 and other
components.
[0019] The illustrated read/write head 102 may be configured as a
MAMR device, and so includes additional components that assist the
read/write transducer 108. A spin-torque oscillator (STO) 122 used
with the read/write transducer 108 which, together with a magnetic
write pole, generates a powerful but localized magnetic field. This
increases the magnetic field over what can be provided by the write
pole itself. As such, a recording medium with higher magnetic
coercivity can be used compared with conventional recording media,
thereby allowing reliable storage of bits in a smaller area on the
medium compared to conventional media.
[0020] The read/write transducer 108 of the read/write head 102
includes one or more read elements, such as a magneto-resistive
stack. The read elements are used to form an electrical signal that
varies with changes in magnetic field on the recording medium 111.
For example, a magneto-resistive element will change resistance in
response to changes in local magnetic field. A current passing
through the element will vary based on the changes in
resistance.
[0021] In FIG. 2, a block diagram illustrates IMR tracks according
to an example embodiment. In this IMR process, bottom tracks
200-202 are first written the recording medium using a bottom track
width 203 and at bottom track pitch 210. Top tracks 204, 205 are
then written partially overlapping between respective bottom tracks
200-202, and therefore are interlaced between the bottom tracks
200-202. The top tracks are written at a top track width 206 and at
top track pitch 208. Note that the tracks 200-202, 204 and 205 are
not multi-level, and the illustrated stacking of tracks is for
purposes of explanation and not intended to be a physical
representation of IMR tracks.
[0022] Because the bottom tracks 200-202 are written at a
relatively large cross-track separation from one another, the
bottom tracks 200-202 can be written using a relatively larger
width 203 than the top tracks 204, 205 without risk of adjacent
track erasure. The larger width 203 enables recording the bottom
tracks 200-202 at relatively higher linear bit density than that of
the top tracks 204, 205. For a HAMR device, the different widths
203, 206 can be achieved by varying laser power to vary the size of
the hotspot in the recording medium. The width and linear bit
density of the top and bottom tracks 204, 205, 200-202 define the
bit-aspect ratio (BAR) of the respective tracks.
[0023] Because individual recording heads and media will have
different characteristics due to manufacturing tolerances, each
drive may have different top and bottom BAR values that are
optimum. In some cases, BAR may be different for different disk
surfaces within a drive, and different for different zones within a
disk surface. For example, in a MAMR drive, a selected combination
of STO power, STO frequency, write coil power, and linear bit
density (which can be controlled by a clock that defines bit
transitions) can produce a selected BAR for a particular recording
regions. Because the STO effect on track width will also have an
effect on adjacent track spacing, the value of track spacing may
also be defined together with the selected BAR. The combination of
linear bit density and track spacing defines the areal density
(ADC) for the region being considered.
[0024] Writing IMR with MAMR can be relatively straightforward
because the track width can be adjusted with a combination of
settings that include microwave power, microwave frequency, and
write coil power. The bottom tracks 201-203 can be written wide and
support a high linear density using a high microwave power and
higher write coil power. The top tracks 204, 205 can be written
narrow with lower microwave power and lower write coil power. The
effect of microwave frequency on the track width can be determined
and tuned for particular combinations of heads and media. Also note
that in some cases, the microwave power may be zero, such that the
head is operating in a CMR mode for one set of the tracks. Bottom
tracks experience double sided squeeze by the two adjacent top
tracks whereas top tracks are non-squeezed since the neighboring
top tracks are two tracks away. Since the top tracks are the only
source of encroachment, the top track write triple and microwave
power may define defines the track pitch of the entire MAMR IMR
system.
[0025] The ADC gain for MAMR IMR is from at least three sources.
First, bottom track linear density can increase due to increased
microwave power. Second, the top track linear density gains from
the non-squeezed conditions. Generally, the top tracks do not
suffer from adjacent track write interference since the next top
track is two tracks away. Third, the track pitch is defined by the
top track write current and microwave power which can be lower than
MAMR CMR and gives a narrower track, thereby enabling high track
density.
[0026] One complication in using IMR relates to the order that
tracks are written. Top tracks can be re-written as many times as
needed but to overwrite a bottom track with top tracks present, the
adjacent top tracks may need to be read and then re-written after
the bottom track is written. A shingled magnetic recording (SMR)
arrangement has similar issues, in that updating a bottom track may
require reading and rewriting any tracks that overlap the bottom
track.
[0027] One way to deal with track writing order is to group top
tracks and bottom tracks into different logical bands. The system
performance penalty for IMR will be similar or less than SMR
because there are at most two tracks that overlap a bottom track.
For SMR, there may be more than two sequentially-written and
overlapping tracks that need to be rewritten in response to
updating a bottom track. The workload of the drive and the
architecture may also favor IMR, e.g., in cases where certain types
of data (e.g., write-once, read-many) can be placed in bottom
tracks to reduce impact on system performance.
[0028] There may be other drive architecture advantages to MAMR IMR
over MAMR SMR related to drive performance. The MAMR SMR ADC gains
are mostly in track pitch while the MAMR IMR ADC gains are in
linear bit density. This means that MAMR IMR can increase data rate
over MAMR SMR. The linear density gain of the bottom track in MAMR
IMR is not achievable with MAMR SMR, even if large microwave powers
are used since IMR uses the straight trimmed track center whereas
MAMR SMR uses the curved track edge. This is shown by the block
diagram in FIG. 3, which shows IMR and SMR tracks that may be
written by a device according to an example embodiment.
[0029] Shingled tracks 300-302 are shown on the left of the figure.
The SMR tracks are shown written from left to right, with track 300
written first, track 301 written next partially overlapping track
300 and track 301, and finally track 302 written partially
overlapping track 301. Because track 301 both overlaps and is
overlapped, it is indicated as being both a top and bottom track
for purposes of this discussion. A read transducer 304 is shown
centered over track 301. Interlaced tracks 310-312 are shown on the
right side of the figure. Bottom track 311 is written first,
followed by top tracks 310, 312 that are interlaced with and
partially overlap edges of the bottom track 311. Read transducer
314 is shown over bottom track 311. Note that for bottom SMR tracks
300, 301, the reader 304 will be centered over a region somewhat to
the left of the originally written track center, whereas for the
bottom IMR track the reader 314 is centered over the originally
written bottom track center. This enables the IMR bottom tracks to
yield better signal for a given track width and linear bit
density.
[0030] An IMR drive can include features to reduce the impact of
the write-order dependence of the bottom tracks. In FIG. 4, a block
diagram shows a MAMR IMR track arrangement according to an example
embodiment. The tracks are separated into at least two different
groups 400, 402, labeled as bottom and top tracks. Each bottom
track is next to top tracks and each bottom track is next to top
tracks as seen in block 404, where the groups of tracks 400, 402
are shown written to a portion of the disk. However, the tracks
within each group 400, 402 may be treated as adjacent tracks during
reading and writing.
[0031] For example, as indicated by block 406, the bottom tracks
400 may be assigned a first logical block address (LBA) range that
is continuous across some or all of the bottom tracks. Similarly,
as shown in block 408, the top tracks 402 may be assigned a second
LBA range that is continuous across some or all of the top tracks.
In this way, the different LBA ranges 406, 408 may be used for
different types of data (e.g., sequential, random,
write-once-read-many, etc.) that minimizes impact on the additional
steps used to update bottom tracks 400. Generally, more active data
(e.g., random data) will be targeted to the top tracks 402, and
more static data (e.g., sequential data) will be targeted to the
bottom tracks 400.
[0032] In order to find an optimum value of the density of the
tracks, the bottom tracks 400 may be written first to determine the
highest linear density possible for this track with the optimized
write current parameters and microwave power. Then linear density
is reduced such that the on-track bit error rate (BER) has a small
BER margin (such as 0.3 decade, for example). The purpose of this
BER margin is to assure the bottom tracks 400 have adequate BER
after the top tracks are written. Then the top tracks 402 are
written using the same head but at a different optimized write
current and microwave power.
[0033] When the bottom tracks 400 are written, there are no
adjacent tracks and therefore no adjacent track interference (ATI),
and the writer can be optimized to boost linear density. For
example, higher microwave power, higher steady state write currents
or write current overshoots can be used for the bottom track. When
the top tracks 402 are written, the bottom tracks 400 will be
trimmed by the top tracks 402, but information at the center of the
bottom tracks 400 will remain. The data on the top tracks 402 in
principle has higher ADC since it is not necessary to provision for
ATI margin.
[0034] In FIG. 5, a flowchart shows a track calibration procedure
according to an example embodiment. This procedure may be performed
in a factory environment, e.g., drive calibration, and may also be
performed in the field, e.g., user configuration or
re-configuration of the drive. The process involves setting 500 a
starting linear density for bottom tracks. Bottom tracks (e.g.,
separated tracks at a bottom-to-bottom track pitch) are written 501
at this density and read back 502 to determine BER of the tracks.
If it is determined at block 503 that the BER is below a maximum
value (e.g., as specified by drive performance target), then the
linear bit density is increased 504, and the writing 501 and
reading 503 are repeated until block 503 returns `yes.`
[0035] When block 503 returns `yes,` the maximum linear bit density
has been found for the bottom tracks, and may be recorded 505 for
future reference. Thereafter, another iteration is performed that
involves reducing 506 the linear bit density, writing 507 and
reading 508 tracks similar to before. In this case, the BER is
tested 509 to determine if it is above a threshold. The threshold
is predefined and generally lower than the maximum allowable BER.
Once the BER is at or below this threshold, block 509 returns `no`
and the bottom track linear density is recorded 510 to be used in
drive operation. Thereafter the procedure continues as shown in
FIG. 6.
[0036] In FIG. 6, a starting top track linear bit density is set
600, and iterations of writing and reading at increasing linear bit
densities of the top track is performed as indicated by blocks
600-604. This is used to obtain a maximum top track linear bit
density, which is recorded 605 and may be used during operation of
the drive together with the bottom track density that was shown
being obtained in FIG. 5. After obtaining the top track linear bit
density, one or more bottom tracks that are overwritten by top
tracks (e.g., tracks written at block 601) are read 606 to find if
the BER has changed past some delta over the previous threshold. If
the BER has gone past this delta as indicated at block 607, then
the linear density of the bottom tracks may be adjusted (e.g.,
decreased) 608 to compensate. Other changes may be made instead of
or in addition to this adjustment 608. For example, track width of
the top tracks may be adjusted (e.g., decreased) along with a
corresponding change (e.g., decrease) in top track linear bit
density.
[0037] In FIG. 7, a diagram illustrates components of a storage
drive apparatus 700 that utilizes one or more read/write heads 712
according to example embodiments. The apparatus includes circuitry
702 such as a system controller 704 that processes read and write
commands and associated data from a host device 706. The host
device 706 may include any electronic device that can be
communicatively coupled to store and retrieve data from a data
storage device, e.g., a computer. The system controller 704 is
coupled to a read/write channel 708 that reads from and writes to
surfaces of one or more magnetic disks 710.
[0038] The read/write channel 708 generally converts data between
the digital signals processed by the system controller 704. The
read/write head 712 includes at least one write transducer and a
read transducer, and at least one of the heads 712 is configured as
a MAMR read/write head. The read/write channel 708 may include
analog and digital circuitry such as decoders, timing-correction
units, error correction units, etc. The read/write channel is
coupled to the heads via interface circuitry 713 that may include
preamplifiers, filters, digital-to-analog converters,
analog-to-digital converters, etc. The read/write channel 708
includes circuitry to activate a STO integrated in the MAMR head
712 during recording to the disk 710.
[0039] The read/write channel 708 may have particular features that
facilitate IMR reading and writing. For example, different channel
configurations (e.g., parameters for write signals, decoding,
timing correction, error correction, etc.) may be used depending on
whether a top or bottom track is currently being written/read. The
read/write channel 708 may be configured to read and write data
differently for different zones of disk 710. For example, some
zones may use different writing formats such as SMR, IMR, and
conventional tracks.
[0040] In addition to processing user data, the read/write channel
708 reads servo data from servo wedges 714 on the magnetic disk 710
via the read/write head. All of the multiple readers of the
read/write head may be used to read servo data, or only a subset
thereof. The servo data are sent to a servo controller 716, which
uses the data to provide position control signals 717 to a VCM 718.
The VCM 718 rotates an arm 720 upon which the read/write heads 712
are mounted in response to the control signals 717. The position
control signals 717 may also be sent to microactuators 724 that
individually control each of the read/write heads 712, e.g.,
causing small displacements at each head.
[0041] An IMR track recording module 730 is stored in memory 711
and is operable to set different recording parameters via the
read/write channel 708 when recording different top and bottom
tracks. For example, bottom tracks are written to the disk
recording medium using a first setting of the MAMR head 712, then
top tracks are written interlaced between and partially overlapping
the bottom tracks using a second setting of the MAMR head. The
second setting resulting in the top tracks being narrower than the
bottom tracks written using the first setting. The first and second
settings may include different combinations of write coil power,
spin-torque oscillator power, and spin-torque oscillator frequency.
Note that in this context, only one of write coil power,
spin-torque oscillator power, and spin-torque oscillator frequency
need be different for the combinations to be different. Also note
that the powers may refer dynamic characteristics of current or
voltage applied to the write pole and/or spin-torque oscillator,
such as steady-state power, rise time, overshoot, etc.
[0042] In reference now to FIG. 8, a flowchart illustrates a method
according to an example embodiment. The method involves writing 800
bottom tracks to a recording medium using a first setting of a MAMR
head. Top tracks are written 801 interlaced between and partially
overlapping the bottom tracks using a second setting of the MAMR
head. The second setting results in a narrower track width than the
first setting. The method optionally involves reading 802 the top
and bottom tracks via one or more read transducers of the MAMR
head. For example, the head may have narrower are wider read
transducers that are each optimized to read one of the top and
bottom tracks.
[0043] Unless otherwise indicated, all numbers expressing feature
sizes, amounts, and physical properties used in the specification
and claims are to be understood as being modified in all instances
by the term "about." Accordingly, unless indicated to the contrary,
the numerical parameters set forth in the foregoing specification
and attached claims are approximations that can vary depending upon
the desired properties sought to be obtained by those skilled in
the art utilizing the teachings disclosed herein.
[0044] The various embodiments described above may be implemented
using circuitry, firmware, and/or software modules that interact to
provide particular results. One of skill in the arts can readily
implement such described functionality, either at a modular level
or as a whole, using knowledge generally known in the art. For
example, the flowcharts and control diagrams illustrated herein may
be used to create computer-readable instructions/code for execution
by a processor. Such instructions may be stored on a non-transitory
computer-readable medium and transferred to the processor for
execution as is known in the art. The structures and procedures
shown above are only a representative example of embodiments that
can be used to provide the functions described hereinabove.
[0045] The foregoing description of the example embodiments has
been presented for the purposes of illustration and description,
and is not intended to be exhaustive or to limit the invention to
the precise form disclosed. Many modifications and variations are
possible in light of the above teaching. Any or all features of the
disclosed embodiments can be applied individually or in any
combination are not meant to be limiting, but purely illustrative.
It is intended that the scope of the invention be limited not with
this detailed description, but rather determined by the claims
appended hereto.
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