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Acoustically Scanned Magnetoresistive Transducer

IP.com Disclosure Number: IPCOM000083100D
Original Publication Date: 1975-Mar-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 29K

Publishing Venue

IBM

Related People

Thompson, DA: AUTHOR

Abstract

Rather than using an array of magnetoresistive heads or using a single travelling head, it is proposed to use a single magnetoresistive head which is acoustically scanned by a sonic wave. The acoustic pulse scans across the head and modulates the magnetic properties of the head, if the head contains magnetostrictive magnetic material. Therefore, the voltage output of the head will vary as the acoustic pulse propagates across the head. If the head has the required bandwidth, and if the speed of the magnetic medium to be read is low enough, then the information which could be obtained by an array of head perpendicular to the direction of track motion can be obtained from a magnetoresistive head with a single magnetoresistive element.

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Acoustically Scanned Magnetoresistive Transducer

Rather than using an array of magnetoresistive heads or using a single travelling head, it is proposed to use a single magnetoresistive head which is acoustically scanned by a sonic wave. The acoustic pulse scans across the head and modulates the magnetic properties of the head, if the head contains magnetostrictive magnetic material. Therefore, the voltage output of the head will vary as the acoustic pulse propagates across the head. If the head has the required bandwidth, and if the speed of the magnetic medium to be read is low enough, then the information which could be obtained by an array of head perpendicular to the direction of track motion can be obtained from a magnetoresistive head with a single magnetoresistive element.

In the drawing, a magnetic head comprises a transducer for providing acoustic pulses and a magnetoresistive stripe, to which is connected a current source that provides a measuring current I(s) through the magnetoresistive stripe. Depending upon the presence and absence of a stray field from a magnetic domain intercepting the magnetoresistive stripe, the resistance of the stripe will change, producing a voltage signal V(s) indicative of the presence and absence of a magnetic domain.

The acoustic transducer can be a piezoelectric type which is positioned to produce a short duration strain pulse which strikes the magnetoresistive stripe, so that different portions of the stripe undergo strain at different times. For instance, strain can be propagated along the length of the magnetoresistive stripe.

An acoustic velocity of 3 x 10/3/ meters/sec and a pulse width of 40 nanoseconds will lead to a section of the stripe 5 mils long, which would be sequentially scanned at a rate of 8 mu sec per mil of length. In the region unde...