Very high sensitivity GMR spin-valve magnetometer

A NiFe/Co/Cu GMR spin-valve magnetometer is designed, built, and tested. Thin-film flux-concentrators provide 50/spl times/ gain, yielding hysteresis-free sensitivity 1/R dR/dH=11%/0e in a 1 mm/sup 2/, internally temperature compensated device. Detection levels of 2 /spl mu/Oe/(Hz)/sup 1/2/ (at 1 Hz) are limited by 1/f resistance noise in the GMR films, which is examined in detail. Improvement by 10/spl times/ is possible via increased device size, as well as lower noise MR films.