Seagate Technology Incorporated

Duane C Phinney

Patrick Joseph Ryan

Allan E Schultz

Peter K George

William P Wood

A wafer level test structure and method detects multiple magnetic domains and magnetic domain instability in a test magnetic element. The apparatus comprises a first MR sensor designed to be held in a single magnetic domain by shape anisotropy and a second MR sensor having a permanent magnet to hold the element in a single magnetic domain. A circuit connects the first and second MR sensors to detect differences between the changes in resistance between the first and second sensors in the presence of a magnetic field or differences in resistance after the application and release of a magnetic field. The circuit is preferably a balance circuit in which imbalance in the presence of a magnetic field indicates the presence of multiple magnetic domains in at least one of the test sensors. Magnetic domain stability may be tested by applying an external field to disrupt the existing single domain state of the test sensors, and thereafter detecting differences in resistance of the sensors during reversal of the magnetic field.

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Saint Paul, MN, United States of America

Duane C Phinney