Giant magnetoresistance materials and their potential as read head sensors

The physical origins of the giant magnetoresistance (GMR) phenomenon is briefly reviewed, and the magnitudes of the GMR ratios in multilayers, spin values, and granular alloys is reviewed. It is pointed out that, though spin valves have been the leading candidate for sensor materials, the maximum values of the sensor sensitivity dR/dH achieved in spin valves are modest. Multilayers can have enormous values of ΔR/R, but are not presently realistic sensor candidates because of their large saturation fields. Arguments are made that interlayer exchange may be manipulable and attractive sensor arrays synthesized. Recent developments in pancake/multilayer granular alloys are presented, NiFe-Ag systems which display a small saturation field and very attractive values of dR/dH. The conclusion is drawn that GMR sensors will be important in read head technology in the near future