Hitachi Global Storage Technologies Netherlands B.v.

Hgst Netherlands, B.v.

Samsung Electronics Co., Ltd.

Western Digital Technologies, Inc.

Western Digital (fremont), Inc.

Xiaodong Che

Xiaoyu Sui

Wen-Chien David Hsiao

Yansheng Luo

Zhen Jin

Terence Tin-Lok Lam

Zhong-heng Lin

Weidong Huang

Michael Paul Salo

Alex Shteyn

Hardayal Singh Gill

Vladimir Nikitin

Yimin Hsu

Weldon Mark Hanson

Roger William Wood

Xiao Z Wu

Michael Alex

Yawshing Tang

Samuel Wei-san Yuan

Herman Ferrier

Jagdeep S Buttar

David D Terrill

Zhihao Li

Kenneth R Davies

Wenchien David Hsiao

Yangsheng Luo

Example read transducers, data storage devices, and methods to provide an angled free layer for generating and decoding multi-level read signals are described. The read transducer includes a free layer having a magnetization bias sensitive to an external magnetic field and the direction of the magnetization bias forms an acute angle relative to a surface of the non-volatile storage medium generating the external magnetic field. The read transducer also includes a pinned layer having a fixed magnetization and a direction of the fixed magnetization forms a right angle with the magnetization bias of the free layer. The read transducer targets a readback location on a track boundary between adjacent tracks and generates a read signal indicative of perpendicular and cross-track fields of the adjacent tracks.

Angled free layer for multi-level read signals

A method, apparatus, and system for implementing channel signal processing assist with an embedded contact sensor (ECS) in hard disk drives. An ECS signal is captured during write and idle operation of the hard disk drive. A read channel monitors changes in the ECS signal providing a clearance monitor function for insuring write integrity.

Implementing channel signal processing assist with ECS contact detection

A perpendicular magnetic write head having improved Bit Error Rate (BER), Adjacent Track Interference (ATI) and Far Track Interference (FTI). The write head includes a write pole and a trailing wrap-around magnetic shield. A permanent magnetic is located at either outer side of the shield. These magnets are magnetized to have magnetizations that are oriented in the same direction, in a direction that is perpendicular to the track direction and parallel with the air bearing surface.

Perpendicular magnetic write head having a trailing wrap-around magnetic shield magnetically biased in a cross track direction

A low flying slider detector is disclosed. In one embodiment a surface is provided. In addition, a suspender is provided for receiving and flying a slider above the surface. A detector is also provided for detecting a low flying slider flying above the surface wherein the detector does not require measuring of the slider fly height to detect the low flying slider and wherein the detecting of the low flying slider is performed at least at a slider level of assembly.

Apparatus and method for detecting low flying sliders

A method for characterizing a magnetic-recording system for the presence of adjacent-track interference and far-track interference. The method includes writing a plurality of repeating pulse-waveforms on a data track of a magnetic-recording disk at a write element of a magnetic-recording head. The method further includes reading a plurality of read-back signals from the magnetic-recording disk over a band of pseudo-data tracks offset from the data track by corresponding pseudo-data-track offsets in a radial direction of the magnetic-recording disk at a read element of the magnetic-recording head. In addition, the method includes displaying a magnetic-recording-signature map synthesized from the read-back signals from the magnetic-recording disk.

Method for characterizing a magnetic-recording system for the presence of adjacent-track interference and far-track interference

A hard disk drive (HDD) including a magnetic disk, the magnetic disk including a data track. The HDD also includes a synchronized rewrite controller for synchronizing a plurality of rewrites of a data pattern on a location of the track of the magnetic disk and the HDD includes a write head controlled by the synchronized rewrite controller for writing the data pattern on the location of the data track and rewriting the data pattern a plurality of times on the location in synchronization with a prior writing of the data pattern on the data track.

Synchronized rewriting of data

Write elements are discussed having a write pole and an associated trailing shield. A leading side of the trailing shield faces a trailing side of the write pole. The leading side of the trailing shield has a shape such that a center portion of the leading side has less of a separation from the trailing side of the write pole than track edge portions of the leading side of the trailing shield. An exemplary shape the leading side of the trailing shield may be a convex shape when viewed from the ABS. The shape of the leading side of the trailing shield causes the trailing shield to shunt less of the magnetic field from the trailing side of the write pole at the track edges so that the written transition at the track edge will not lag behind the written transition at the track center allowing for a straighter transition.

Shaped trailing shield of a perpendicular recording write element

A hard disk drive that determines a flying height from a slope of a line created from a ratio of amplitudes of frequencies in response to impulse functions. A first set of amplitudes of reference frequencies can be determined from a reference impulse. A second set of amplitudes of data frequencies can be determined from a data impulse during operation of the disk drive. Ratios of amplitudes of the data and reference frequencies at different discrete frequencies can be plotted. The slope of the plotted line corresponds to the difference between the flying height when the reference impulse is generated and the flying height when the data impulse is generated. The disk drive may utilize the slope in a feedback routine to control the flying height.

Flying height measurement and control with user data signal

A disk drive that protects stored data from stray magnetic fields is disclosed. Sensors for sensing stray magnetic fields are mounted to the base and/or cover of the drive and aligned with the trajectory of the movement of the read/write head. If the sensors, which have memory such as a toggle switch, are exposed to a high stray magnetic field, operation of the drive is suspended until a follow-up algorithm or protocol is implemented. The sensors can sense specific direction of stray fields. The sensor can change resistance if a high stray field is detected. The information in the sensors is collected and processed by the drive controller.

System, method, and apparatus for monitoring stray magnetic fields and protecting disk drives therefrom

A magnetic structure for use in a magnetic recording head, the structure having improved resistance to stray field writing. The magnetic structure can be for example a magnetic shield or a return pole of a perpendicular write element. The structure includes a main body portion which may have a generally rectangular configuration, and first and second wing portions extending laterally from the sides of the body at or near the ABS. The wing portions have a depth measured perpendicular to the ABS that is significantly less than the depth of the body portion (preferably less than 25 percent of the body portion). The wing portions may also have notches formed in their ABS edges. The wings conduct flux from the ABS edge of the body portion and create a flux choking effect for magnetic flux flowing into the wings.

Winged pole and shield structure for reducing stray field in a perpendicular write head

Method calibrates an assembled hard disk drive for read head accessing rotating disk surface, by estimating non-linearity of that playback device based on two data patterns, which have a short transition-pair waveform and a long transition-pair waveform. By linearly constructing a simulated long transition-pair waveform from the short transition-pair waveform and aligning it with the long transition-pair waveform, non-linear distortion is estimated, creating the transfer curve as product of this process. The transfer curve is used to compensate the read data of a track to create the adjusted read data, which is used to decode the track being read. The adjusted read data is the product of this process. The hard disk drive including the transfer table. Second method using transfer table to create adjusted read data for track, the processor, embedded circuit and hard disk drive implementing this method. Manufacturing embedded circuit as product.

Apparatus and method for internal calibration of normalized playback transfer curve in a hard disk drive

An apparatus for reader characterization is described. The apparatus includes a rotator for rotating a media. The media can contain a signal having a value for a function of a read/write head being assessed. The rotator is operable in conjunction with said apparatus. The apparatus also includes a proximator for proximalizing the media to the read/write head. The proximator is operable in conjunction with said apparatus. The apparatus further includes a writer operable in conjunction with said assembly. The writer writes the signal upon the media. The signal emits the value of the function. The signal is detectable by a reader of the read/write head. The apparatus additionally includes an interface operable in the apparatus for providing removable orientation of the read/write head in an assessing position. The assessing position enables a reader of the read/write head to detect the signal upon rotation of the signal through the assessing position.

Magnetic reader recording characterization at slider or bar level

A hard disk drive (HDD) detects and measures external stray magnetic fields with existing HDD components. After detecting a strong external magnetic field, read and write operations of the HDD are suspended, and/or other proper corrective actions are taken to minimize loss of data. To measure the stray magnetic field, the magnetic head reader is used as a field sensor. The resistance of the reader changes in the presence of the field, such as with the preamp in the HDD. The resistance also changes with temperature. If the temperature inside the HDD is measured, the resistance change due to temperature is normalized. Even without being able to measure the HDD temperature, the stray magnetic field can be measured with a top head and a bottom head in the HDD. The temperature sensitivity of the reader is thereby cancelled out.

System, method, and apparatus for in-situ stray magnetic field measurement

A system and method for determining head-disk contact (HDC) in a magnetic recording disk drive uses the signal from the magnetoresistive (MR) read head. The analog MR signal is digitized and input to a digital signal processor with circuitry and/or software for integrating the signal amplitude over a low-frequency range. The calculated value from the integration when the slider is out-of-contact with the disk is a reference value. The same integration is then performed during operation of the disk drive and the measured value is compared to the reference value. If the measured value exceeds the reference value by some predetermined amount, this is an indication of the onset of HDC or that HDC has occurred. The method can be used in head-disk testers to facilitate the design and testing of disk drive components, such as slider-suspension assemblies and fly-height actuators located on the slider to alter the head-disk spacing, and in disk drives to control fly-height actuators and to take corrective action prior to HDC.

System and method for determining head-disk contact in a magnetic recording disk drive

A system and method for calibrating and controlling a magnetic recording disk drive fly-height actuator uses the signal from the magnetoresistive (MR) read head to determine head-disk contact (HDC). The MR signal is measured over a low-frequency range, with the slider out-of-contact with the disk, to develop a reference value. The MR signal is then measured over the same low-frequency range and if it exceeds the reference value by some predetermined amount, this is an indication of HDC. The fly-height actuator control signal value for HDC is recorded and thus corresponds to a head-disk spacing of zero. The calibration method also determines the sensitivity of head-disk spacing to the fly-height actuator control signal by measuring a series of MR read signal amplitudes for a corresponding series of control signals. The fly-height actuator is calibrated from the sensitivity and the value of control signal that results in zero head-disk spacing, and can then be controlled to move the head to a desired fly height and maintain it at the desired fly height.

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Saratoga, CA, United States of America

Xiaodong Che