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-$X$ Co 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 ${\alpha }_1$ (Fe–Co rich phase) and ${\alpha }_2$ (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 ${\alpha }_1$ and ${\alpha }_2$ . 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.