Polycrystalline current-perpendicular-to-plane giant magnetoresistance pseudo spin-valves using Co₂Mn(Ga_0.25Ge_0.75) Heusler alloy

We have studied the structure and magnetoresistive properties of polycrystalline current-perpendicular-to-plane giant magnetoresistance pseudo spin-valves (PSVs) with Co₂Mn(Ga_0.25Ge_0.75) (CMGG) ferromagnetic layers and a Ag spacer. With (110) textured CMGG thin films and (111) textured Ag spacer, the PSVs annealed at 350 °C with 2 nm CoFe buffer layers showed ΔRA of 3.7 m Ω μ m 2 and MR ratio of 12.2%, while the PSVs without the buffer layer showed ΔRA of only 1.3 m Ω μ m 2. High angle angular dark field images showed that the drop of ΔRA by annealing was due to the deterioration of the multi-layer CMGG/Ag/CMGG structure. Energy-dispersive X-ray spectroscopy images further confirmed the interdiffusion between CMGG layer and the Ag layer outside the CMGG/Ag/CMGG trilayer. In addition, we discuss the difference in the magnetoresistive properties of polycrystalline and epitaxial PSVs.