International Business Machines Corporation

Western Digital Technologies, Inc.

David Malcolm Hannon

Albert John Wallash

Earl Albert Cunningham

Steven Harry Voss

Jeffrey B Brown

Nickolas Christopher Apuzzo

Raymond Patrick Mallette

Paul Sheldon Tyler

Samir Elias Abboud

Hung Liang Hu

Donald E Horne

Jodie Ann Christner

Gary L Dunbar

Timothy D Bouwkamp

James Weispfenning

The present invention may be regarded as a disk drive with protection against damage due to a thermal asperity. The disk drive comprises a disk having a surface with an asperity, and a magneto-resistive head actuated radially over the surface of the disk for generating a read signal comprising a thermal asperity component caused by the magneto-resistive head contacting the asperity on the surface of the disk. A bias generator is provided for generating an electrical bias applied to the magneto-resistive head, and a thermal asperity detector detects the thermal asperity component in the read signal. When the thermal asperity component is detected, the electrical bias is reduced for a time interval, thereby protecting the magneto-resistive head.

Disk drive comprising thermal asperity protection by reducing an electrical bias supplied to a magneto-resistive head

The magnetic states of MR reproducing heads are reinitialized during media drive manufacturing by applying initializing magnetic fields to the transducers after they have been manufactured and incorporated into media drive assemblies.

Magnetic reinitialization of thin film magnetoresistive reproducing

A capacitive sensor for detecting capacitive contrast servo information on a disk in a data recording disk file includes a center-tapped inductor connected to a high frequency oscillator, a sensing probe formed on the back side of the slider and electrically coupled to one end of the inductor, and a dummy probe also formed on the back side of the slider and electrically connected to the other end of the inductor. The center-tapped inductor forms a primary coil of a transformer so that variations in capacitance sensed by the sensing probe provide a differential output signal in the inductor which is sensed by the transformer secondary coil. The probes, and their electrically conductive leads and terminal pads, are formed by thin film deposition techniques on the back side of the slider and are located with respect to the inductive read/write head so as to equally receive any noise generated by the read/write head. The dummy probe is spaced away from the air bearing surface of the slider so that the variation in capacitance due to the capacitive contrast pattern on the disk is received only by the sensing probe.

Capacitive sensor for head positioning in magnetic recording disk files

Two parallel conductors are positioned on top of a magnetic layer where bubble domains are to be coded. The two parallel conductors are positioned to form a gap therebetween of a particular size. An external in-plane magnetic field is applied to the magnetic layer. The size of the gap is selected such that when current is simultaneously applied in both conductors, a local in-plane field will be formed in the gap which is sufficient for coding bubble wall states and a vertical field will be formed in the gap sufficient to retain a bubble in the gap during the application of current to the conductors. The application of current in the one direction in the conductors codes a bubble with one pair (S = 0) of Bloch lines and the application of current in the opposite direction codes a bubble with no Bloch lines (S = 1).

Method and apparatus for the controlled generation of wall encoded

A device adapted for biasing bubble domains in a low externally applied magnetic bias field. This device is suitable for use when isolated bubbles or a column of bubbles are translated to or from a bubble lattice. The device has a pair of parallel channels, each containing a stripe domain therein. Positioned between the pair of channels is a channel for the translation of isolated bubbles. Positioned in juxtaposition with the bubble containing channel and the pair of stripe containing channels are a pair of parallel conductors. The passage of current through one conductor in one direction and a current through the other conductor in the opposite direction together with the presence of the stripe domains in the two channels provide a biasing field around the channel containing the bubbles which permits the isolated bubble operating margin to overlap the lattice operating margin.

Device for biasing bubble domains

A device adapted for use in a low externally applied magnetic field, for example, 15 Oe, with a bubble lattice system is described. The device has a Y shaped channel in which bubbles are propagated between a bubble lattice column and either detector means or generator means. The magnetic pattern surrounding the Y shaped channel is controlled to yield a self biasing magnetic field which enables the device to retain the advantages of the close bubble packing in a bubble lattice for the detection and generation operations.

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Palo Alto, CA, United States of America

David Malcolm Hannon