Inverse giant magnetoresistance at room temperature in antiparallel biased spin valves and application to bridge sensors

We report a spin-engineering scheme whereby the sign of the giant magnetoresistance in an antiparallel biased spin valve may be selected by varying only layer thicknesses within the structure. The antiferromagnetic coupling in the biased layers leads to either positive exchange bias or positive magnetoresistance in the response of the structure. Hence, spin valves may be fabricated with either positive or negative sensitivities to applied fields in the same sense. When two spin valves of each type are connected in the appropriate Wheatstone bridge configuration, a sensor with four active legs may be constructed. The bias may be set by either the growth field, or by application of uniform field to the entire sensor structure in a single postprocessing anneal step. (C) 1999 American Institute of Physics. [S0003-6951(99)00750-0].