Temperature dependence of spin-dependent transport properties of Co2MnSi-based current-perpendicular-to-plane magnetoresistive devices

The origin of magnetoresistance (MR) ratio reduction below similar to 80 K in Co2MnSi (CMS)/Ag/Co2MnSi current-perpendicular-to-plane giant magnetoresistive devices was investigated. The temperature dependence of Delta RA 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 degrees interlayer exchange coupling, which originated from inter-diffused Mn impurities in the Ag spacer, was observed only at low temperatures from 5 to similar to 100 K. A possible origin for the reduction in the MR ratio below similar to 80 K is the drastic reduction in the spin-diffusion length of the Ag spacer due to magnetic ordering of the Mn impurities.