Giant magnetoresistance in Ag1−xNix−yFey heterogeneous alloy films

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Abstract
We have investigated the effects of phase segregation and compositional variation on the giant magnetoresistance(GMR) observed in heterogeneous AgNiFe alloy films. The films were sputtered from a mosaic Ag/NiFe/Fe target onto glass substrates at the system ambient temperature. They had a thickness of 200–300 nm, and were rapidly thermally annealed (RTA) under vacuum in order to promote phase segregation. By altering the amount of Fe in the target mosaic, the Ni:Fe ratio was systematically varied from 80:20 to 34:66 atomic percent. The Ag concentration for all films was fixed at 78±5 atomic percent. The GMR was maximized using a RTA temperature of 650 °C. Annealing at higher temperatures decreased the saturation field of the GMR, but also lowered its size. Changing the film composition had little effect on the saturation field of the GMR, but for both as‐deposited and optimally annealed samples the magnetoresistance was found to decrease as the Ni concentration decreased.