International Business Machines Corporation

Haralambos Lefakis

Bruce Alvin Gurney

Virgil S Speriosu

Dennis R Wilhoit

Robert Fontana

James K Howard

David Eugene Heim

James Hsi-Tang Lee

Omar U Need, Iii

Daniele Mauri

Kevin Robert Coffey

Stuart Stephen Parkin

Joachim Gerhard Clabes

Gary W Rubloff

Paul S Ho

Peter O Hahn

A magnetic recording system uses an improved spin valve magnetoresistive (SVMR) sensor. The SVMR sensor has a self-pinned laminated layer as the pinned ferromagnetic layer in place of the conventional single-layer pinned layer. Because this laminated layer is 'self-pinned', a hard bias or exchange bias layer is not needed. The self-pinned laminated layer has at least two ferromagnetic films antiferromagnetically coupled to one another across a thin antiferromagnetically (AF) coupling film. Since the two ferromagnetic films in this laminated layer have their magnetic moments aligned antiparallel, their two magnetic moments can be made to essentially cancel by making the two ferromagnetic films of substantially the same thickness. The magnetic field energy generated by the signal field acting on this laminated layer will be significantly less than the effective anisotropy energy of the laminated layer. This is because the former is proportional to the difference in thicknesses of the two ferromagnetic films in the laminated layer, while the latter is proportional to the sum of the thicknesses. As a result, the laminated layer will not rotate in the presence of the signal field, but will be 'self-pinned'. The elimination of the exchange bias layer previously required for pinning also eliminates the need for Ni--Mn and its associated high-temperature process.

Spin valve magnetoresistive sensor with self-pinned laminated layer and

A magnetoresistive read sensor based on the spin valve effect in which a component of the read element resistance varies as the cosine of the angle between the magnetization directions in two adjacent magnetic layers is described. The sensor read element includes two adjacent ferromagnetic layers separated by a nonmagnetic metallic layer. A layer of nonmagnetic electrically conductive material is deposited adjacent to and in contact with one of the ferromagnetic layers, referred to as a filter layers to form a back or conduction layer which provides a low resistance path for conduction electrons transmitted through the adjacent filter layer. The thickness of the filter layer is selected such that it effectively blocks conduction electrons having spins antiparallel to the direction of magnetization in the filter layer while allowing conduction electrons with parallel spins to be transmitted through the layer into the adjacent back layer. The magnetization of the filter layer is free to rotate in response to an applied magnetic field thereby effectively varying the electrically resistance to conduction electrons in the back/filter layer. The thickness of the back layer is selected to optimize the sensor parameters being measured and is in a range of about 4.0 A to 1000 A.

Magnetoresistive spin valve sensor having a nonmagnetic back layer

A magnetic recording data storage system of high recording density is made possible by an improved magnetoresistive sensor. The sensor has a ferromagnetic sensing layer that is a laminated layer of two ferromagnetic films antiferromagnetically coupled to one another and separated by an antiferromagnetically coupling film. By appropriate selection of the thickness of the nonmagnetic antiferromagnetically coupling film, the ferromagnetic films become antiferromagnetically coupled and their magnetizations rotate as a single rigid unit in the presence of the external magnetic field to be sensed. The ferromagnetic sensing layer can be used in conventional magnetoresistive sensors of the anisotropic magnetoresistive (AMR) type and in spin valve magnetoresistive (SVMR) sensors. In the spin valve sensor, the laminated ferromagnetic sensing layer serves as the free layer and is preferably formed of two films of nickel-iron (Ni-Fe) separated by a ruthenium (Ru) antiferromagnetically coupling film. Because the two ferromagnetic films have their moments aligned antiparallel, then, assuming the two films are made of the same material, by selecting the two films to have different thicknesses the effective free layer thickness can be reduced without significantly reducing the magnetoresistance.

Magnetoresistive sensor with improved ferromagnetic sensing layer and

A magnetoresistive (MR) read transducer comprising a thin film MR layer formed of ferromagnetic material and a nonmagnetic thin film spacer layer in contact with the MR layer. The spacer layer comprises a material selected from the group consisting of nichrome and nichrome with chromium oxide. A thin film of soft magnetic material is deposited in contact with the spacer layer so that a transverse bias is produced in at least a part of the MR layer. A feature of the invention is that the resistivity of the spacer layer can be chosen by selecting the ratio of nichrome to chromium oxide in the spacer layer. In a specific embodiment the spacer layer extends over only the central region of the MR layer. In case the MR layer is a nickel based alloy, a wet chemical etching process using an etchant comprising an aqueous solution of ceric ammonium nitrate and acetic acid can be used to pattern the spacer layer.

Method for making a magnetoresistive read transducer

A technique is described for improving metal-organic substrate adhesion and for reducing stress between the metal film and the substrate. Low energy reactive ions, electrons, or photons are incident upon the substrate to alter the surface chemistry of the substrate to a depth of from about 10 angstroms to a few hundred angstroms. The energy of the incident reactive ions and electrons is about 50-2000 eV, while the energy of the incident photons is about 0.2-500 eV. Irradiation of the substrate can occur prior to or during metal deposition. For simultaneous metal deposition/particle irradiation, the arrival rates of the metal atoms and the substrate treatment particles are within a few order of magnitude of one another. Room temperatures or elevated temperatures are suitable.

Metal-polymer adhesion by low energy bombardment

A magnetoresistive (MR) read transducer comprising a thin film MR layer formed of ferromagnetic material and a nonmagnetic thin film spacer layer in contact with the MR layer. The spacer layer comprises a material selected from the group consisting of nichrome and nichrome with chromium oxide. A thin film of soft magnetic material is deposited in contact with the spacer layer so that a transverse bias is produced in at least a part of the MR layer. A feature of the invention is that the resistivity of the spacer layer can be chosen by selected the ration of nichrome to chromium oxide in the spacer layer. In a specific embodiment the spacer layer extends over only the central region of the MR layer. In case the MR layer is a nickel based alloy, a wet chemical etching process using an etchant comprising an aqueous solution of ceric ammonium nitrate and acetic acid can be used pattern the spacer layer.

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San Jose, CA, United States of America

Haralambos Lefakis