An apparatus comprises a laser diode configured to generate light during a write operation. A slider comprises a near-field transducer (NFT) and an optical waveguide. The slider is configured for heat-assisted magnetic recording and to communicate the light to the NFT via the waveguide. A writer heater of the slider is configured to receive power during the write operation. A thermal sensor is situated at or near an air bearing surface of the slider. The thermal sensor is configured to produce a sensor signal in response to sensing back-heating from the medium while the NFT generates heat during a write operation. Circuitry, coupled to the thermal sensor, is configured to compare the sensor signal to a threshold and generate an output signal indicative of degradation of NFT performance in response to the sensor signal exceeding the threshold.

An apparatus comprises a laser diode configured to generate light during a write operation. A slider comprises a near-field transducer (NFT) and an optical waveguide. The slider is configured for heat-assisted magnetic recording and to communicate the light to the NFT via the waveguide. A writer heater of the slider is configured to receive power during the write operation. A thermal sensor is situated at or near an air bearing surface of the slider. The thermal sensor is configured to produce a sensor signal in response to sensing back-heating from the medium while the NFT generates heat during a write operation. Circuitry, coupled to the thermal sensor, is configured to compare the sensor signal to a threshold and generate an output signal indicative of degradation of NFT performance in response to the sensor signal exceeding the threshold.

According to one embodiment, a disk device includes a disk-shaped recording medium, a magnetic head including a write head, a read head, and a heater, and a controller including a reference signal generator outputting a reference signal having a constant voltage amplitude at the same frequency as a high-frequency component of a gap measurement signal recorded in the recording medium, a measurer measuring a component amplitude of a reproduced signal of the gap measurement signal and an amplitude of the reference signal, and a heater controller controlling a power value of heater power supplied to the heater based on the measured values of the component amplitude and the amplitude of the reference signal.

According to one embodiment, a magnetic disk device includes a magnetic disk, a magnetic head that includes a write head configured to write data to the magnetic disk, a read head configured to read data from the magnetic disk, and a heater configured to adjust a flying height of the write head, and a controller that includes a first detection unit configured to detect the flying height of the write head, a second detection unit configured to detect a positioning error of the magnetic head with respect to a track of the magnetic disk, and a memory configured to store a first threshold and a second threshold.

According to one embodiment, a magnetic disk device includes a magnetic disk, a magnetic head that includes a write head configured to write data to the magnetic disk, a read head configured to read data from the magnetic disk, and a heater configured to adjust a flying height of the write head, and a controller that includes a first detection unit configured to detect the flying height of the write head, a second detection unit configured to detect a positioning error of the magnetic head with respect to a track of the magnetic disk, and a memory configured to store a first threshold and a second threshold.

Systems and techniques relating to voltage signal peak level detection used in sensor devices, namely in Fly-Height Sensors (FHS) devices include, according to an aspect, an integrated chip device comprising: peak detection circuitry configured to receive a voltage signal and output a peak voltage signal associated with a peak voltage level of the voltage signal, wherein the peak detection circuitry comprises: a linear loop section configured to store the peak voltage level and hold additional voltage levels of the voltage signal at an output terminal of an amplifier to a value greater than zero; and a feedback loop section configured to reduce a leakage current within the peak detection circuitry and generate a guard voltage signal usable to reduce a feedback voltage and prevent the feedback voltage from successively re-entering into the feedback loop section.

Gain values used by a variable gain amplifier (VGA) to read servo marks of a heat-assisted recording medium are measured. Sector-specific, repeatable gain values that indicate an expected VGA gain at a desired clearance are determined based on the measured gain values. The sector-specific, repeatable gain values are used as input to a closed-loop clearance controller together with measured values of servo VGA gain while writing data to the recording medium.

A data storage device is disclosed comprising a head actuated over a disk, wherein the head comprises a fly height actuator configured to control a fly height of the head over the disk. A plurality of host read commands are received from a host, and a performance metric associated with accessing the disk to execute the host read commands is measured. When the performance metric indicates the data storage device is operating with a performance margin, the fly height actuator is controlled to increase the fly height of the head over the disk, wherein the performance metric consists of at least one of a throughput of the host read commands and a power consumption of the data storage device.

An apparatus comprises a slider configured for heat-assisted magnetic coupled to a controller. The slider comprises a writer, a heater, a near-field transducer, and an optical waveguide for communicating light from a laser diode to the near-field transducer. The controller is configured to set a target pre-write clearance of the slider prior to performing a write operation, set a target write clearance of the slider for performing the write operation, and determine a difference between the target pre-write and write clearances to define a target pre-write clearance offset. The controller is also configured to measure, for a plurality of different target pre-write clearance offsets, a writability metric for the slider while sweeping a laser diode current, and adjust the target pre-write clearance offset so that the writability metric reaches a predetermined threshold. The controller is further configured to perform subsequent write operations using the adjusted target pre-write clearance offset.

An idle sweep routine for a hard disk drive involves a series of servo-controlled one-Nth (1/N) equivalent sub-band random seeks in one radial direction, followed by another series of servo-controlled one-Nth equivalent sub-band random seeks in the other radial direction, where a complete band refers to the complete set of user-data tracks and a one-Nth sub-band refers to a contiguous 1/N portion of the complete band. For example, a first series of sub-band random seeks may be in the disk outer diameter (OD) to inner diameter (ID) direction, followed by a second set of sub-band random seeks in the ID to OD direction. Based on disk scratch and Si smear robustness, sub-band random seeks are found effective in moving the sider over a significant number of tracks during each seek to likely inhibit disk lubrication degradation and avoid thermal asperities during such an idle sweep routine.