Structure and magnetoresistive properties of current-perpendicular-to-plane pseudo-spin valves using polycrystalline Co_2Fe-based Heusler alloy films

摘要

We report current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) of pseudo-spin valves (PSVs) with polycrystalline Co_2Fe(Al_(o.5)Si_(0.5)) (CFAS) and Co_2Fe(Ga_(0.5)Ge_(0.5)) (CFGG) Heusler alloy films. Strongly [011] textured polycrystalline Heusler alloy films grew on the Ta/Ru/Ag underlayer. Relatively large CPP-GMR values of ARA up to 4 mQ |xm~2 and AR/R up to 10% were obtained with 5 nm thick Heusler alloy films and Ag spacer layer by annealing CFAS PSV at 450 °C and CFGG PSV at 350 °C. Transmission electron microscopy revealed a flat and sharp interface between the [011] textured CFAS layers and the [111] textured Ag spacer layer. Annealing above an optimal temperature for each PSV led to reductions in MR values as a result of the thickening of the spacer layer induced by the Ag diffusion from the outer Ag layers.