Giant magnetoresistance and phase decomposition of Fe–XCr–Co (WFe/WCo=1) thin film granular alloys

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Abstract
In this study, the giant magnetoresistance (MR) effect was observed in Fe–XCr–Co (WFe/WCo=1, X=27, 40, 50, 60, 70, and 80 wt %) ternary heterogeneous alloy films. After aging, the separated phases and lattice images of the α1 (Fe–Co rich phase) and α2 (Cr rich phase) were further determined by high resolution transmission electron microscope. Experimental results indicate that the MR variations in Fe–Cr–Co thin films alloys were associated with the heterogeneous microstructure. By isothermal aging at 550 °C for 80 min, the largest MR of −43% appears for the film with the composition of 40(Fe/Co)–60Cr at 77 K under a field of 14 kOe. At the same treatment condition, the MR ratios of 50(Fe/Co)–50Cr and 30(Fe/Co)–70Cr are −13.2% and −21.3%, respectively. Cr content, therefore, significantly affected the MR ratio.