Polycrystalline current-perpendicular-to-plane giant magnetoresistance pseudo spin-valves using Co_2Mn(Ga_(0.25)Ge_(0.75)) Heusler alloy

摘要

We have studied the structure and magnetoresistive properties of polycrystalline current-perpendicular-to-plane giant magnetoresistance pseudo spin-valves (PSVs) with Co_2Mn(Ga_(0.25)Ge_(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 ℃ with 2nm CoFe buffer layers showed ARA of 3.7mΩ μm~2 and MR ratio of 12.2%, while the PSVs without the buffer layer showed ARA of only 1.3 mΩ μm~2. High angle angular dark field images showed that the drop of ARA 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.