Seagate Technology Incorporated

Won Choul Yang

Shi Jung Kim

Ju Yong Lee

Jon David Trantham

Tim Rausch

John West Dykes

Dong Wook Lee

Clifford Jayson Bringas Camalig

Mui Chong Chai

Haejung Lee

Jung Wook Hur

Jin Pil Kim

A method includes moving a heat-assisted magnetic recording head relative to a magnetic recording medium comprising a plurality of tracks, the head comprising a reader and a writer including a near-field transducer (NFT) optically coupled to a laser diode, the writer comprising a center which is laterally offset relative to a center of the reader to define a writer-reader offset (WRO) therebetween. Patterns are written to a particular track at a plurality of laser diode current levels. The patterns are read and a WRO value is calculated at a peak amplitude position for each of the laser diode current levels. A slope of the WRO values is determined with the laser current diode levels. A health condition of the NFT is determined by determining if the slope is greater than a predetermined threshold indicative of non-uniform activation across the NFT.

Health monitoring for head of a heat-magnetic recording device using a writer-reader offset

Health monitoring for head of a heat-assisted magnetic recording device using a writer-reader offset

An AC signal having a specified frequency and a DC offset voltage is applied to a slider substrate or a magnetic recording medium. A low- or non-modulation interface is defined between the slider and medium. In response to applying the AC signal, an oscillation in an electrostatic force occurs between the slider and the medium at the specified frequency, which causes an oscillation in thermal sensor signal at the slider, which oscillates at the specified frequency. A heater of the slider is adjusted to decrease spacing between the slider and medium during oscillation of the electrostatic force. For each heater adjustment, thermal sensor resistance is measured over a specified number of medium revolutions. Head-medium contact is detected using one of an amplitude of a harmonic of the thermal sensor signal and a summation of amplitudes of all frequency components at the specified frequency.

Head-medium contact detection using a thermal sensor and surface charge control of a slider

A current temperature of a data storage device having a heat assisted recording (HAMR) device is measured while in idle. A threshold laser diode power output of the HAMR device is calculated at the current temperature when there is a change between a previous temperature and the current temperature. A new laser diode current that produced the calculated threshold laser diode power output is applied to the HAMR device when there is a change between the currently applied laser diode current and the new laser diode current.

Adaptive laser output control in a HAMR device

An apparatus comprises a read/write head having a heater, wherein a low- or non-modulation interface is defined between the head and a magnetic recording medium. A microactuator is coupled to the head. A main actuator is coupled to the microactuator and the head. A controller is coupled to the main actuator, the microactuator, and the head. The controller is configured to control movement of the main actuator and the microactuator in response to a position error signal. The controller is further configured to induce an oscillation in the heater at a predetermined frequency. A detector is coupled to the controller. The detector is configured to sense a disturbance in the PES supplied to the microactuator resulting from the induced heater oscillation, and detect contact between the head and the medium using the PES disturbance.

Head-medium contact detection using high frequency heater oscillation

A method of controlling laser output in a heat assisted magnetic recording device can be performed by control circuitry in a data storage device. The method includes measuring a temperature, measuring laser output power of a laser, determining a power error by subtracting an optimal laser output power from the measured laser output power and comparing the power error to at least one threshold to determine whether an applied current to the laser needs to be adjusted. The at least one threshold is related to how great the power error can be while maintaining the integrity of data on a recording medium.

Controlling laser output in a HAMR device

An apparatus comprises a slider that includes a fly height sensor. A signal generator is coupled to the slider. The signal generator is configured to generate an AC electrical signal having a DC offset voltage and to adjust the DC offset of the AC electrical signal to a plurality of DC offset voltages. Circuitry is coupled to the fly height sensor and the signal generator. The circuitry is configured to measure fly height of the slider in response to application of the AC electrical signal with varying DC offset voltages to the slider. The circuitry is further configured to determine an extremum of the measured fly heights and generate an output that includes the DC offset voltage associated with the fly height extremum.

Apparatus and method for measuring surface charge of a slider

The disclosure is related to an apparatus and methods for addressing variations in bit error rates amongst data storage segments. In a particular embodiment, an apparatus includes a controller that detects variations in bit error rates amongst different segments of a plurality of segments in a storage medium. The controller also adjusts a read/write operation parameter according to the detected variations amongst the bit error rates in the plurality of segments.

Addressing variations in bit error rates amongst data storage segments

At least one laser input current is applied to a laser in a heat assisted magnetic recording device. Laser output power of the laser is measured at the at least one applied laser current. A relationship is characterized amongst temperature, applied laser input current and laser output power. Laser current is set to an optimal laser current as determined at manufacturing. A metric of recording performance is measured to determine if the relationship is acceptable.

Characterizing laser output in a HAMR device

Technologies are described herein for adaptive write pole tip protrusion compensation in a storage device having magnetic recording media. Variations in temperature of a head of a storage device are measured for various combinations of values of write-channel parameters during multiple test writes to the recording media. Sensitivity of the head temperature to change in value of the write-channel parameters is determined from the temperature measurements. A ratio of change in write pole tip protrusion of the head to change in head temperature is also determined. From the sensitivity of the head temperature to change in value of the write-channel parameters and the ratio of change in write pole tip protrusion of the head to change in head temperature, a coefficient corresponding to each write-channel parameter is calculated for the head to be utilized in a write pole tip protrusion compensation mechanism of the storage device.

Adaptive write pole tip protrusion compensation

Technologies are described herein for recovering an instable head in a storage device using an internal head heater. An instability in the reader head may be detected, and, in response to detecting the instability, a thermal shock may be applied to the reader head utilizing the head heater to recover the head.

Growing community of inventors

Hong Kong, China

Won Choul Yang