Spin transfer switching of current-perpendicular-to-plane giant magnetoresistance with various Gd-Fe free-layer compositions

We have investigated the spin transfer switching (STS) properties of current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with various compositions of Gd-Fe free-layers for magneto-optical light modulator applications, whereby iron (Fe) concentrations are varied from 72.5 to 80.3 at. %. Switching current densities decreased dramatically with increases in Fe concentration within the Gd-Fe compound. The switching current density (Jc0) for a device with composition Gd Fe80.3 at.% was 20.5 MA/cm2, which is more than eight times smaller than that for devices with composition Gd Fe72.5 at. %. This reduction in switching current can be attributed to a decrease in the effective perpendicular anisotropy in Fe-richer Gd-Fe compounds.

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