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Scanned Magnetoresistive Sensors

IP.com Disclosure Number: IPCOM000083458D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 3 page(s) / 49K

Publishing Venue

IBM

Related People

Lean, EG: AUTHOR [+2]

Abstract

A type of scanned magnetoresistive sensor, based on the generation of a localized static strain in a magnetoresistive head, is provided which avoids use of RF oscillators to provide acoustic power, pulse generators, to produce narrow pulses for high-resolution heads and a broad hand acoustical transducer of the type described by C. H. Bajorek et al in an article entitled "Six Acoustic Transducers for Acoustically Scanned Magnetoresistive Sensors", IBM Technical Disclosure Bulletin, Vol. 17, No. 11, April 1975, pages 3498 to 3500.

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Scanned Magnetoresistive Sensors

A type of scanned magnetoresistive sensor, based on the generation of a localized static strain in a magnetoresistive head, is provided which avoids use of RF oscillators to provide acoustic power, pulse generators, to produce narrow pulses for high-resolution heads and a broad hand acoustical transducer of the type described by C. H. Bajorek et al in an article entitled "Six Acoustic Transducers for Acoustically Scanned Magnetoresistive Sensors", IBM Technical Disclosure Bulletin, Vol. 17, No. 11, April 1975, pages 3498 to 3500.

Control circuits, such as a shift register, diode array, tapped electromagnetic delay line and tapped acoustic delay line are fabricated directly on a substrate as illustrated.

An array of metallic electrodes, of width an~ spacing a, is fabricated on a proper substrate. A piezoelectric film (AlN or PnO) of thickness d is deposited on the array. The magnetoresistive stripe, such as a magnetostrictive Ni-Co alloy, of thickness t approx.= 200 Angstroms is vapor-deposited on the film. The metallic electrodes are connected individually to the tapped delay line circuit.

A voltage pulse, of duration Delta t, propagating with velocity v occupies a length Delta 1 in the delay line. This pulse causes the metallic electrodes to be sequentially charged, thus producing a local, static strain in the piezoelectric film. The magnitude of this strain is given by Lambda = ev/cd, where e and c are the proper piezoelectric and elastic constants of the piezoelectric film, b is the film's thickness, and v is the magnitude of the applied voltage pulse.

With v = 1 vol~, g = 0.2 Mu m and typical values of e = 1 and c = 10/11/ Newton/m /2/ Lambda= 5 x 10/-4/. In typical Ni-Co films in which the magnetic anisotropy field is of the order of 30 O(e). this strain is equivalent to an effective magnetic field of almost 40 O(e). The resulting magnetoresistive effect can therefore be observed.

Shift registers, operating...