Wd Media, LLC

Western Digital Technologies, Inc.

Harold H Gee

Andreas Moser

Mark A Nichols

Dragos I Mircea

Steven E Lambert

Mrugesh Desai

Erhard Theodor Schreck

Pierre-Olivier Jubert

Sukumar Rajauria

Thien Nguyen

Daniel S Wolf

Toan Tang

Douglas N Bartholomew

Eric Roddick

A data storage device is disclosed comprising a head actuated over a magnetic media, wherein the head comprises a write coil, a laser configured to heat the magnetic media during a write operation, and a read element. A test pattern is written to the magnetic media by applying a current to the write coil and a first bias to the laser. A second bias is applied to the laser while the head passes over the test pattern, and then the test pattern is read from the magnetic media using the head to generate a first read signal. A first noise power of the first read signal is measured, and at least one parameter of a noise power function is generated based on the first noise power measurement, wherein the noise power function is a function of at least the bias applied to the laser.

Data storage device measuring HAMR media distributions

A data storage device is disclosed comprising a head actuated over a disk, wherein the head comprises a write assist element. Data is written to the disk using the write assist element. A protrusion of the head toward the disk is measured periodically, and an abnormality with the write assist element is detected when a slope of the protrusion measurements indicates the protrusion is increasing.

Data storage device detecting abnormality with a write assist element based on slope of protrusion

Systems and methods for improving the accuracy of test measurements involving aggressor tracks written to the disks are provided. One such method involves erasing a circumferential band of a disk, writing a central track on the circumferential band, measuring and storing a first track profile of the central track, writing an aggressor track on each side of the central track at a preselected aggressor track offset from the central track, measuring and storing a track profile of the aggressor tracks at the preselected aggressor track offset, measuring and storing a second track profile of the central track, performing the prior actions exactly n times where n is greater than or equal to 1, determining an estimated distance between the aggressor tracks based on the respective track profiles, determining a selected measurement using the estimated distance between the aggressor tracks, and the first and second track profiles of the central track.

Systems and methods for improving accuracy of test measurements involving aggressor tracks written to disks of hard disk drives

Methods for measuring media performance associated with adjacent track interference are provided. One such method includes iteratively writing data to a target track for each of a plurality of n frequencies, measuring a first signal amplitude and a first noise for each of the n sectors on the target track, writing an aggressor track pattern proximate the target track, measuring a second signal amplitude and a second noise for each of the n sectors on the target track, calculating a weighted sum for each of the signal amplitude measurements for each of the plurality of n frequencies, and calculating a weighted sum for each of the noise measurements for each of the plurality of n frequencies, and repeating the writing the aggressor track pattern, the measuring the second signal amplitude and the second noise, and calculating the weighted sums for preselected numbers of times.

Methods for measuring media performance associated with adjacent track interference

Systems and methods for making fast measurements of channel performance metrics such as error margin and off-track recording capability in shingled magnetic recording are provided. One such method involves writing a plurality of shingled tracks on the disk, measuring an off track read capability (OTRC) of each of the plurality of shingled tracks, determining radial endpoints of the measured OTRC for each of the plurality of shingled tracks, determining an approximate radial center for each of the plurality of shingled tracks based on the respective OTRC radial endpoints, and measuring a channel performance metric at a range centered around the approximate radial center for each of the plurality of shingled tracks. In one such case, the channel performance metric involves error margin. One such system includes a processor coupled to a memory, a magnetic transducer, and a test platform, where the processor is configured to perform the method.

Systems and methods for fast measurement of channel performance metrics such as error margin and off-track recording capability in shingled magnetic recording

Systems and methods for improving accuracy of head positioning using existing servo patterns are provided. In one embodiment, a method for improving read head positioning is provided that comprises: writing a series of tracks over a range of read offsets to be calibrated; measuring a set of raw track profiles from the series of tracks; sampling the set of raw track profiles at a series of signal amplitude levels; constructing a reference track profile from the set of sampled track profiles; calculating a set of read offset deltas from each sampled track profile; merging the sets of read offset deltas into a set of average read offset deltas; and converting the set of average read offset deltas into a read offset correction table. A similar method for improving disk write head positioning is also provided which utilizes such a read offset correction table to eventually create write offset correction table.

System and method for improving head positioning

Cross-track density capability is predicted for a large number of writes based on a plurality of erase band width measurements. Over the plurality of erase band width measurements, a number of writes in a series of writes performed as part of an aggressing track sequence is varied. A model of the magnetic track width (MTW) as function of the number of writes employed in the MTW measurements may be generated and an estimate of the erase band width for a large number of writes derived from the model as a prediction of cross-track density capability.

Predictive characterization of adjacent track erasure in recording media

A wide area track erasure (WATER) rate of change is determined from a model generated from a plurality of track erasure measurements performed on a magnetic recording media. A model of the change in noise amplitude for an off-track position as a function of the number of aggressor track writes employed in the track erasure measurements is generated. In a log-linear space a linear fit of the change in noise amplitude with respect to the number of aggressor track writes yields a rate of noise amplitude change (dB/decade) which may be utilized to rank magnetic recording media.

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San Jose, CA, United States of America

Harold H Gee