Temperature dependence of spin-dependent transport properties of Co ₂MnSi-based current-perpendicularto-plane magnetoresistive devices

The origin of magnetoresistance (MR) ratio reduction below ∼80 K in Co₂MnSi (CMS)/Ag/Co₂MnSi current-perpendicular-to-plane giant magnetoresistive devices was investigated. The temperature dependence of ΔRA was independent of the CMS layer thickness, indicating that the spin-diffusion length in the CMS layers is unimportant for the reduction in the MR ratio at low temperatures. A small 90° interlayer exchange coupling, which originated from inter-diffused Mn impurities in the Ag spacer, was observed only at low temperatures from 5 to ∼ 100 K. A possible origin for the reduction in the MR ratio below ∼80K is the drastic reduction in the spin-diffusion length of the Ag spacer due to magnetic ordering of the Mn impurities.