Western Digital Technologies, Inc.

Hgst Netherlands, B.v.

Hitachi Global Storage Technologies Netherlands B.v.

Kei Yasuna

Guoxiao Guo

Masahito Kobayashi

Keiichiro Nonaka

William Bernard Boyle

Minoru Hashimoto

Shaomin Xiong

Duc H Banh

Masaki Yoshioka

Masaru Furukawa

Makoto Takase

Yun Hong

Ryohheita Hattori

Thomas R Albrecht

Erhard Theodor Schreck

Satoshi Yamamoto

Qinghua Zeng

Fuminori Sai

Hideki Zaitsu

Edgar D Sheh

Keishi Takahashi

Kohji Takasaki

Tomoyuki Oyama

So Ogiwara

Tomoo Ozaki

Dan Wang

Due H Banh

Shuji Nishida

Takao Horiguchi

Thambirajah Suthasun

Suthasun Thambirajah

Ichiro Yokokawa

Yoshio Soyama

Various illustrative aspects are directed to a data storage device, method, and one or more processing devices that are configured to: obtain a first value of a first servo burst signal and a second value of a second servo burst signal associated with a servo pattern in a track of the disk; calculate an adjusted first value and an adjusted second value by adjusting one or both of the first value and the second value based on a measure of servo pattern distortion associated with the track; generate a position error signal (PES) using the adjusted first value and the adjusted second value; and control a position of the head over the track using the PES.

Data storage device with servo burst signal correction for mitigating effects of servo pattern distortion

Various illustrative aspects are directed to a data storage device, method, and one or more processing devices that are configured to: determine an initial track pitch based on a performance metric determined for the head; determine a track pitch adjustment based on a measure of servo pattern distortion associated with a region of the disk; and set a final track pitch for the region of the disk based on the track pitch adjustment and the initial track pitch.

Data storage device with track pitch determination for mitigating effects of servo pattern distortion

Various illustrative aspects are directed to a data storage device including one or more disks, an actuator mechanism configured to position a selected head among one or more heads proximate to a corresponding disk surface among the one or more disks, the selected head comprising a write element and an assistive energy emitter, and one or more processing devices configured to, individually or in combination: apply an assistive energy current to the assistive energy emitter while refraining from applying a write current to the write element, and vary a level of the assistive energy current over time while refraining from applying the write current to the write element.

Energy-assisted magnetic recording data storage device with opportunistic boosted laser pre-biasing

Various illustrative aspects are directed to a data storage device, method, and one or more processing devices that are configured to: write a plurality of test servo patterns using a plurality of different write settings; select one of the plurality of different write settings based on analyzing the plurality of test servo patterns for mode hop; and write a plurality of final servo patterns using the selected one of the plurality of different write settings.

Data storage device with embedded mode hop predictor patterns

Various illustrative aspects are directed to a data storage device, method, and one or more processing devices that are configured to: determine a first burst value based on a first set of bursts within a servo pattern, the first set of bursts comprising two bursts having a first length in a longitudinal direction of a track containing the servo pattern and at least one burst having a second length in the longitudinal direction of the track and different than the first length; determine a second burst value based on a second set of bursts within the servo pattern, the second set of bursts comprising at least two bursts having the second length; generate a position error signal (PES) based on the determined first burst value and the determined second burst value; and control a position of at least one head among the one or more heads based on the PES.

Data storage device with symmetric split burst servo pattern

Various illustrative aspects are directed to a data storage device, comprising one or more disks; an actuator mechanism configured to position one or more heads proximate to a corresponding disk surface of the one or more disks; and one or more processing devices. The one or more processing devices are configured to: select a sector on the corresponding disk surface to which to write data, wherein the sector is selected in accordance with a data erosion mitigation pattern; and output, while the head is positioned proximate to a preceding sector that precedes the selected sector, a laser pre-bias current to a laser-generating component of the head, wherein the laser pre-bias current is sufficient to induce significant data erosion on the preceding sector.

Data storage device with enhanced management of laser pre-bias and logic block addressing in heat-assisted magnetic recording

Various illustrative aspects are directed to a data storage device, comprising: one or more disks; an actuating mechanism comprising one or more heads, and configured to position the one or more heads proximate to disk surfaces of the one or more disks; and one or more processing devices. The one or more processing devices are configured to: determine a first burst value based on an averaged value of a first set of one or more bursts; determine a second burst value based on an averaged value of a second set of one or more bursts; generate a position error signal (PES) based on the determined first burst value and the determined second burst value; and control a position of at least one head among the one or more heads based on the PES.

Data storage device with split burst servo pattern

Various illustrative aspects are directed to a data storage device, comprising: one or more disks; an actuator assembly comprising a head, and configured to position the head over a corresponding disk surfaces; and one or more processing devices, wherein the head comprises: a write element; a laser unit; and a fly height control element, and wherein the one or more processing devices are configured to: iteratively perform write start operations of write start patterns with the head on the corresponding disk surface, at a plurality of values of at least one of laser pre-bias current, and write backoff; detect pattern signal amplitudes of the write start patterns on the corresponding disk surface; and determine a relation of write backoff to laser pre-bias current for the head, based at least in part on the pattern signal amplitudes.

Determining laser induced thermal protrusion and laser threshold in heat-assisted magnetic recording (HAMR) data storage

Various illustrative aspects are directed to a data storage device, comprising: one or more disks; an actuator assembly comprising a head, and configured to position the head over a corresponding disk surface; and one or more processing devices, the head comprising: a write element; a laser unit; and a fly height control element, and wherein the one or more processing devices are configured to: iteratively perform spiral write operations of spiral patterns comprising a plurality of sync marks with the head on the corresponding disk surface, wherein the spiral write operations are performed at: a plurality of values of laser pre-bias current, write backoff, and/or start disk phase; detect pattern signal amplitudes of the spiral patterns on the corresponding disk surface; and determine a relation of write backoff to laser pre-bias current for the head, based on the pattern signal amplitudes of the spiral patterns.

Method to measure thermal protrusion by sensing spacing change due to pre-lasing

A data storage device is disclosed comprising a head actuated over a disk. The head is used to read servo information from the disk and generate a position error signal (PES) representing a position of the head over the disk. A control signal is generated based on the PES and a triangle-shape dither signal, and the head is positioned over the disk using the control signal.

Data storage device employing triangle-like dither to spread track squeeze

A system and method of writing servo write tracks to a rotating disk using a head having a read/write offset is disclosed. One embodiment utilizes a write element on the head to write the servo write tracks. A read element on the head is then positioned over the servo write tracks. The phase of a specific frequency component of the track shape error in the servo write track is measured during the positioning of the read element over the servo write track. A sine wave having a specific frequency and a phase is selected based on the measurement results. The sine wave is then applied to a servo system as a correction signal. A new servo write track is then written with the write element.

Disk drive and method of writing servo write tracks to a disk

Embodiments described herein provide for robust servo patterns that comply with planarization constraints and also allow use of a single master template for manufacture of both the front and back of a magnetic disk. Planarization constraints are met because only a portion of servo data is hard patterned on the magnetic disk and the hard patterned servo data areas comply with planarization constraints. The servo pattern has two symmetrical servo write assist patterns, one on each side of a central burst pattern. The servo sync, SAM, track-ID, sector-ID, and/or RRO values can be written magnetically by the write head onto these servo write assist patterns after the completion of the planarization process. The symmetric design of the servo pattern allows both a left-to-right and a right-to-left servo write and read back, thereby enabling use of a single master template in magnetic disk manufacture.

Servo pattern compatible with planarization constraints of patterned media and use of a single master template

Embodiments described herein provide for patterned media concentric zones with an alternating series of concentric servo zones and overlap zones. The overlap zones facilitate the writing of servo data between servo zones of different servo frequency. The overlap zones may be dual frequency zones. The dual frequency zones have a first set of overlap patterns with the substantially identical pattern as the bordering lower frequency servo zone and a second set of overlap patterns with the substantially identical pattern as the bordering higher frequency servo zone. A bootstrap zone can be included near the inner diameter to assist initial servo writing. Alternatively the overlap zones are bootstrap zones. Such bootstrap zones have both bootstrap patterns and overlap patterns, the overlap patterns have the substantially identical pattern as a bordering servo zone. Bootstrap patterns only require DC magnetization for servo operability.

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Fujisawa, Japan

Kei Yasuna