Development of a high precision absolute linear displacement sensor utilizing GMR spin-valves

We describe the development of a novel linear displacement sensor utilizing Giant Magnetoresistance (GMR) elements. This device is based on the division of a magnetically soft layer of a spin valve device into two anti-parallel magnetic domains. The total resistance of the spin-valve varies linearly with displacement of the domain wall because of different resistances of the aligned and anti-aligned magnetic states of the spin-valve. Domain wall translation is achieved by the use of a magnetic wall "trap" generated by permanent magnets. Displacement is thus related directly to the device resistance.