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Resistance Matching for Coupled Film Magnetoresistive Elements

IP.com Disclosure Number: IPCOM000083273D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Lin, CC: AUTHOR [+2]

Abstract

In a coupled-film magnetoresistive (MR) head, such as disclosed in U.S. Patent Patent No. 3,860,965, issued January 14, 1975, it is a requirement that both MR elements have exactly the same dimensions to provide common mode rejection, especially the suppression of noise spikes due to temperature excursions of the head caused by contact with medium asperities or dust particles.

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Resistance Matching for Coupled Film Magnetoresistive Elements

In a coupled-film magnetoresistive (MR) head, such as disclosed in U.S. Patent Patent No. 3,860,965, issued January 14, 1975, it is a requirement that both MR elements have exactly the same dimensions to provide common mode rejection, especially the suppression of noise spikes due to temperature excursions of the head caused by contact with medium asperities or dust particles.

The dimension which is most difficult to reproduce with close tolerances is the thickness of the MR films and it is, therefore, desirable to make common mode rejection independent of this dimension. This is achieved by fabricating each MR stripe together with the resistor, which controls the current carried by it in the same deposition, i.e., MR1 and R1 are deposited simultaneously, and so are MR2 and R2.

Voltages generated by temperature changes are suppressed by the combination of two MR stripes, two resistors and differential amplifier DA, since the concurrent resistivity changes in the two MR stripes have the same sign; the magnetic transitions in the medium, on the other hand, are sensed, since the two elements bias each other in opposite directions and the resistivity changes caused in them by an external magnetic field have opposite signs. In addition, the DC voltage seen by the differential amplifier is small, the residual voltage being due to the difference between the demagnetizing fields inside the two elements and, h...