Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: Given that there is a limit to the extent to which a record head may be excited before its pole tips saturate (gap fuzziness) while overwriting a second set of information signals atop a first set of information signals recorded in a high coercivity recording medium, the present invention concerns the discovery that if the record gap is dimensioned to equal approximately the flux change length that corresponds with a 2 f signal (FCL.sub.2) recorded atop a 1 f signal, i.e. if the record gap is somewhere between about 0.7 and 1.5 times the flux change length associated with the 2 f signal, erasure of the 1 f signal (as well as other signals) will be most effective.