Mechanism of large magnetoresistance in Co2MnSi/Ag/Co2MnSi devices with current perpendicular to the plane

Fully epitaxial current-perpendicular-to-plane giant magnetoresistance (MR) devices with half-metallic Co2MnSi (CMS) electrodes and a Ag spacer were fabricated to investigate the relationship between the chemical ordering in CMS and its MR properties, including bulk and interface spin-asymmetry coefficients beta and gamma. CMS/Ag/CMS annealed at 550 degrees C shows the largest MR ratio: 36.4% and 67.2% at RT and 110 K, respectively. An analysis based on Valet-Fert's model reveals large spin asymmetry (gamma>0.8) at the CMS/Ag interface, which contributes predominantly to the large MR ratio observed. First-principles ballistic conductance calculations for (001)-CMS/Ag/CMS predict a high majority-spin electron conductance, which could be the origin of the large gamma observed in this study.