Komag Corporation

Wd Media, LLC

Western Digital Technologies, Inc.

Western Digital (fremont), Inc.

Maxtor Corporation

David E Wachenschwanz

Gerardo Bertero

David Treves

Andrew M Homola

Christopher H Bajorek

James L Chao

Sudhir S Malhotra

Chun Sei Tsai

Thomas Anthony O'Dell

Carl E Barlow

Michael McNeil

David E Fowler

Donald C Stafford

John Vicars

Zhengsheng Shan

Paul Christopher Dorsey

Andreas Moser

Michael Alex

Bogdan Florin Valcu

Min Yang

Wen Jiang

Chirag C Patel

Balvinder Singh

Emur M Velu

Boon Sien Chew

Bernard E Knigge

The present disclosure generally relates to a HAMR head and techniques and apparatus for HAMR writer pole length characterization. One or more bits may be magnetically written on a disk using a leading edge of the writer pole at a first polarity. The disk may be moved under a body of the writer pole to magnetically write the one or more bits in the disk at a second polarity that is opposite to the first polarity to generate a feedback pulse having a signal amplitude. The signal amplitude of the feedback pulse may be measured as a function of writing frequency. A first effective length of the writer pole may be determined based on the measurements.

HAMR writer pole length characterization

A disk drive is disclosed comprising a disk comprising a plurality of data tracks, and a head actuated over the disk, the head comprising an asperity sensor operable to generate a sensor signal having a magnitude based on a bias setting of the asperity sensor. The asperity sensor is configured with a first bias setting and a first asperity on the disk is detected based on the sensor signal generated at the first bias setting. The asperity sensor is configured with a second bias setting different from the first bias setting and a second asperity on the disk is detected based on the sensor signal generated at the second bias setting.

Disk drive detecting different asperities on a disk using different sensor bias settings

It is determined whether one or more heads of a data storage device (DSD) have been within a radial position of one or more disks of the DSD for more than a threshold period of time. When it is determined that the one or more heads have been within a radial position of the one or more disks for more than the threshold period of time, the one or more heads are radially moved by more than a predetermined distance to reduce a development of variations in a distribution of lubricant on a first surface of the one or more disks.

Disk lubricant management in data storage device

A disk drive is disclosed comprising a head actuated over a disk, the head comprising a touchdown sensor comprising a resistance. A bias signal is applied at a reference value to the touchdown sensor at a reference temperature, and a corresponding reference resistance of the touchdown sensor is measured. An operating value for the bias signal is generated based on a predetermined operating temperature of the touchdown sensor, the reference resistance, the reference temperature, and a thermal coefficient of resistance (TCR) of the touchdown sensor, wherein the TCR specifies a change in temperature of the touchdown sensor relative to a change in the resistance of the touchdown sensor.

Disk drive calibrating bias signal for touchdown sensor

A magnetic disk media is physically preformatted to have a non-user data area providing any of a servo pattern, a gray code pattern and a timing line pattern. The non-user data area patterns are preformatted to have non-recordable regions with a radial width that is always less than the track pitch of the data area. In exemplary implementations, servo patterns, gray code patterns and timing line patterns are physically preformatted to have a recordable:non-recordable radial width ratio substantially equal to that of a user data area. In certain embodiments, non-magnetic or magnetically suppressed regions having cross-track dimension substantially equal to that of spaces between tracks in the user data area are consecutively offset in a cross-track direction from the discrete track recording pattern of the user data area.

Patterns for pre-formatted information on magnetic hard disk media

A method of forming a discrete track recording pattern on a soft magnetic underlayer of a perpendicular magnetic recording disk. In one embodiment, the soft magnetic underlayer is continuous throughout the discrete track recording pattern.

Perpendicular magnetic recording disk with a soft magnetic layer having a discrete track recording pattern

Perpendicular magnetic discrete track recording disk

A method of forming a discrete track recording pattern in a magnetic recording disk. In one embodiment, the discrete track recording pattern may be formed in a NiP layer continuous throughout the discrete track recording pattern. Alternatively, the discrete track recording pattern may be formed in a substrate.

Method of fabricating a magnetic discrete track recording disk

A magnetic recording system includes a patterned medium comprised of land areas and trough areas, a write element which writes the data to the patterned medium, and a read element which reads the data from the patterned medium and servo information from the troughs. The land areas store data and the trough areas inhibit storage of data. The read element is wider than the write element.

Patterned medium and recording head

A discrete-track-recording (DTR) disk (also called 'patterned' disk) has a sectored servo formed by modulation of its sidewalls in a predetermined manner, whereas sidewalls of data sectors are not modulated in this manner. Each servo sector has two side walls that are each respectively modulated in two different ways. Hence, a readback signal from a given servo sector contains components of each of the two different modulations, even in case of 'DC' erase initiation. Therefore, the just-described modulated servo sectors eliminate servowriting. Moreover, data signals are read without filtering the modulation, because data sector sidewalls are not modulated.

Modulation of sidewalls of servo sectors of a magnetic disk and the resultant disk

A magnetic recording medium includes a substrate, an underlayer, a lower magnetic layer formed on the underlayer, an intermediate layer, and an upper magnetic layer formed on the intermediate layer. The intermediate layer is typically Ru, and promotes anti ferromagnetic coupling between the upper and lower magnetic layers. The upper and lower magnetic layers are typically Co alloys. The lower magnetic layer has a high saturation magnetization Ms to promote high exchange coupling between the upper and lower magnetic layers. The dynamic coercivity of the lower magnetic layer is lower than the exchange field to ensure rapid switching of the lower magnetic layer.

Magnetic media with improved exchange coupling

A magnetic recording medium includes a substrate, an underlayer, a lower magnetic layer formed on the underlayer, an intermediate layer, and an upper magnetic layer formed on the intermediate layer. The intermediate layer is typically Ru, and promotes antiferromagnetic coupling between the upper and lower magnetic layers. The upper and lower magnetic layers are typically Co alloys. The lower magnetic layer has a high saturation magnetization Ms to promote high exchange coupling between the upper and lower magnetic layers. The dynamic coercivity of the lower magnetic layer is lower than the exchange field to ensure rapid switching of the lower magnetic layer.

A perpendicular magnetic recording disk having a soft magnetic film disposed between a substrate and a magnetic recording layer. The soft magnetic film includes a soft magnetic underlayer and one or more layer groups having a spacer layer and a soft magnetic layer disposed above the spacer layer in each layer group. The spacer layers induce anti-ferromagnetic coupling between the surrounding ferromagnetic layers. The spacer layers may be comprised of ruthenium. The soft magnetic layers may have a granular decoupled structured through the use of a segregate.

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Saratoga, CA, United States of America

David E Wachenschwanz