Effect of heat treatment and Co on the giant magnetoresistance of Fe-60 Cr–XCo alloy thin films

This article presents the giant magnetoresistance (GMR) effect and microstructure of Fe-60Cr-XCo ternary heterogeneous alloy films. After ion beam sputtering, the films are heat treated at a temperature within the miscibility gap. The separated phases and lattice images of the α1 (Fe–Co rich phase) and α2 (Cr rich phase) are further determined by high resolution transmission electron microscopy. In the granular alloy, the GMR effect is obtained by the interface scattering between the phases of α1 and α2. By isothermal aging at 550 °C for 80 min, the largest MR ratio of −62% appears for the film with the composition of Fe-60Cr-15Co at 77 K under a field of 14 kOe. For the same treatment, the MR ratios of Fe-60Cr-10Co and Fe-60Cr-20Co are −39% and −43%, respectively. The Co content and heat treatment condition in the alloy system obviously affect the MR ratio.