Observation of giant magnetoresistance in a Heusler alloy spin valve

We have observed giant magnetoresistance in spin valves using the PtMnSb Heusler alloy as either one or both of the two ferromagnetic component layers. Up to 0.5% MR has been measured in the CIP geometry in films consisting of (111) epitaxial PtMnSb grown on Al₂O₃ with Cu as a non-magnetic spacer and Co as the remaining ferromagnetic component. Attempts to pin the upper Co layer with the high coercivity ferromagnet Co₈₀Pt₂₀ helped decouple the magnetic layers but led to increased current shunting lowering the overall MR. We have also grown PtMnSb(111)/CuMnSb(111)/PtMnSb(111)/MnFe spin valves. Such spin valves showed a maximum GMR of 0.05%. We attribute this low value of MR to insufficient decoupling of the PtMnSb layers and possible interlayer mixing between the different Heusler alloys