Abstract: Various illustrative aspects are directed to a data storage device comprising: a voice coil motor (VCM) and one or more processing devices, configured to actuate the VCM, switch on measuring a back electromotive force (BEMF) from the VCM for intervals of an initial BEMF measurement that are free of spikes in the initial BEMF measurement, and process a measured BEMF signal from the intervals of the initial BEMF measurement that are free of spikes in a change of current term of the initial BEMF measurement.

Abstract: Various illustrative aspects are directed to a data storage device comprising: a voice coil motor (VCM) and one or more processing devices, configured to actuate the VCM, switch on measuring a back electromotive force (BEMF) from the VCM for intervals of an initial BEMF measurement that are free of spikes in the initial BEMF measurement, and process a measured BEMF signal from the intervals of the initial BEMF measurement that are free of spikes in a change of current term of the initial BEMF measurement.

Abstract: 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.

Abstract: 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.

Abstract: A data storage device is disclosed comprising a head actuated over a magnetic media comprising a plurality of tracks. A first pattern of magnetic transitions is written to a first segment of a first track. Preparation is made to write a second pattern of magnetic transitions to a second segment of a second track adjacent the first segment of the first track. When the second pattern matches the first pattern, a write boost is configured to a first setting, and when the second pattern does not match the first pattern, the write boost is configured to a second setting. The second pattern of magnetic transitions is then written to the second segment of the second track using the configured write boost.

Abstract: A data storage device is disclosed comprising a head actuated over a disk surface by an actuator arm. The actuator is controlled to press the actuator arm against a crash stop in order to write a plurality of bursts on the disk surface each with a different write parameter setting. Each burst is read in order to measure a quality metric for each burst, and an operating setting for the write parameter is configured based on the measured quality metrics.

Abstract: A data storage device is disclosed comprising a head actuated over a magnetic media comprising a plurality of tracks. A first pattern of magnetic transitions is written to a first segment of a first track. Preparation is made to write a second pattern of magnetic transitions to a second segment of a second track adjacent the first segment of the first track. When the second pattern matches the first pattern, a write boost is configured to a first setting, and when the second pattern does not match the first pattern, the write boost is configured to a second setting. The second pattern of magnetic transitions is then written to the second segment of the second track using the configured write boost.

Abstract: A data storage device is disclosed comprising a head actuated over a magnetic media. A write boost is configured to a first setting, and a first pattern of magnetic transitions is written to a first servo field of a servo sector on the magnetic media using the first setting for the write boost. The write boost is configured to a second setting different from the first setting, and the first pattern of magnetic transitions is written to a second servo field of the servo sector on the magnetic media using the second setting for the write boost.

Abstract: A data storage device is disclosed comprising a head actuated over a disk, wherein the head comprises a spin torque oscillator (STO). A first bias signal is applied to the STO during a first interval preceding a write operation to write data to the disk, wherein the first bias signal causes the STO to protrude toward the disk. After the first interval, a second bias signal is applied to the STO during a second interval spanning at least part of the write operation, wherein an amplitude of the first bias signal is in the range of 1.1 to 1.5 times an amplitude of the second bias signal.

Abstract: A servo writer is disclosed operable to write servo sectors on a disk to define non-circular servo tracks. The servo writer comprises control circuitry including a servo control system operable to measure a position of a head over the disk to generate a position signal, generate a position error signal (PES) representing a difference between the position signal and a reference signal, process the PES with a servo compensator to generate a control signal, and position the head over the disk in response to the control signal. A disturbance is induced into the servo control system, and while positioning the head over the disk in response to the control signal, a plurality of servo sectors are written on the disk to define a servo track, wherein the disturbance induced into the servo control system causes the servo track to be non-circular relative to a rotation axis of the disk.

Abstract: A system to detect a ramp position is disclosed. The system includes a head positioner coupled to an actuator arm to position a head relative to a disk and a controller to: control the head positioner to move the head toward the ramp; determine a plurality of integrator values while moving the head; generate a threshold based on the plurality of integrator values; and determine the ramp position based on a first integrator value exceeding the threshold.