International Business Machines Corporation

Kenneth Ting-Yuan Kung

Ching Hwa Tsang

Po-Kang Wang

Mao-Min Chen

Mohamad Towfik Krounbi

Robert Fontana

Denny D Tang

James Hsi-Tang Lee

Jyh-Shiliey Jerry Lo

A magnetoresistive (MR) sensor comprising a layer of ferromagnetic material forming an MR sensing element wherein the MR sensor is biased by utilizing only the MR stripe uniaxial anisotropy and the shape anisotropy of the active region of the sensing element. The active region of the MR element has a generally square geometry to provide the desired shape anisotropy. The MR sensor is biased at approximately 45 degrees by defining the magnetization at the four edges of the sense element active region utilizing its shape anisotropy and canting the magnetic easy axis at an appropriate angle during fabrication of the MR sensor. To minimize Barkhausen noise, a single magnetic domain configuration is achieved by reducing the sensor active region dimensions, i.e., stripe height and track width, to less than the characteristic domain wall thickness such that the formation of multiple magnetic domains is no longer energetically favorable. A magnetic biasing material such as a layer of antiferromagnetic material to provide exchange coupling, can be provided at a pair of opposing edges to maintain the magnetization at the edges in the desired orientation and to stabilize the sensor.

Edge-biased magnetoresistive sensor

An exchange-biased magnetoresistive (MR) read transducer in which the MR layer composition is changed at the interface with an antiferromagnetic layer, which is in direct contact with the ferromagnetic MR layer. The exchange-bias field strength H.sub.UA in the MR layer is increased at room temperature by adding a specially-optimized transition region in the ferromagnetic MR layer at the interface. The percentage of iron in the ferromagnetic alloy varies from a higher value at the interface to a lower value at the opposite end of the transition region. The higher iron ratio at the antiferromagnetic interface enhances the exchange-bias field H.sub.UA and the lower iron ratio throughout the bulk of the ferromagnetic MR layer maintains the lower coercivity preferred in the layer, thereby enhancing the longitudinal bias field with respect to the MR coercivity. Advantageously, the enhanced longitudinal bias effect of the special ferromagnetic transition region does not reduce the critical temperature T.sub.cr at which the temperature-dependent exchange-bias field H.sub.UA (T) approaches zero.

Magnetoresistive sensor employing an exchange-bias enhancing layer

Magnetoresistive sensor employing an exchange-bias enhancing layer with

A magnetoresistive (MR) read transducer having passive end regions separated by a central active region in which an MR layer is formed over substantially only the central active region and in which a magnetic bias layers is formed in each passive end region. Each of the magnetic bias layers includes a layer of ferromagnetic material and a layer of antiferromagnetic material overlaying and in contact with the ferromagnetic layer to provide an exchange-coupled magnetic bias field. Each of the magnetic bias layers form an abutting junction having magnetic and electrically continuity with the MR layer to produce a longitudinal magnetic bias field in the transducer.

Method of manufacturing magnetoresistive read transducer having a

A magnetoresistive (MR) read transducer assembly having passive end regions separated by a central active region, and a method of fabricating it. Layers of a first biasing material and a nonmagnetic decoupling spacer material are deposited on a substrate, then covered by a mask only in the central region. By etching or ion milling, those parts of the layers not covered by the mask are removed to define a transverse biasing means in the central region and define the passive end regions. With the same mask remaining in place, a conductive material and exchange layer comprising a second biasing material are deposited over all regions. The mask is removed to define and provide conductor leads and longitudinal biasing means only in the end regions. MR material is thereafter deposited as a continuous thin film in direct contact with the central region containing the transverse biasing means and in direct contact with the end regions containing the longitudinal biasing means. This fabrication technique has no critical etching steps requiring stopping at or near a particular interface and the MR film provides a continuous platform for carrying current without butted junctions in the current path.

Method of fabricating a magnetoresistive read transducer

A nonvolatile magnetoresistive (MR) storage device comprising a plurality of MR storage elements, each comprising a substrate and a multilayered structure including two thin film layers of ferromagnetic material separated by a thin layer of nonmagnetic metallic conducting material. The magnetization easy axis of both ferromagnetic layers in each storage element is oriented substantially lengthwise of the storage elements and substantially parallel to the direction of an applied sense current. The magnetization direction of one of the ferromagnetic layers is fixed in a direction substantially lengthwise of the storage elements, and the magnetization direction of the other layer is free to switch between two digital states in which the magnetization is substantially parallel or substantially antiparallel to the magnetization direction in the one layer.

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San Jose, CA, United States of America

Kenneth Ting-Yuan Kung