Giant Magnetoresistive Sensors

Giant Magnetoresistive Ratio (GMR) materials will be used to model, specify, and design monolithic magnetic field sensors for detecting motion of ferromagnetic bodies and low magnetic fields. Magnetic fields in the 10-8 to 10 gauss are of primary interest. Three kinds of GMR multilayers will be examined: 1) antiferromagnetic-coupled multilayers, 2) spin-valve or symmetrical spin-valve multilayers which use "pinning", and 3) unpinned magnetic layers sandwiching a conducting interlayer. Four sensor configurations will be examined: 1) shield/flux concentrators with no bias, 2) an on-chip permanent magnet bias, 3) an on-chip integrated electromagnetic circuit bias, and 4) a self-biasing technique. In Phase I modeling based on materials measurements will be used to select the best GMR multilayer structure and the best sensor configuration. Also in Phase I, development models of this sensor with discrete signal conditioning electronics will be characterized by at least one government laboratory and by two companies who have expressed interest in the military applications of these sensors. In Phase II monolithic prototype sensors with integrated circuit underlayers will be designed, fabricated, and characterized in collaboration with commercial and government laboratories in anticipation of transfer to production.