The effect of substitution of Fe with Cr on the giant magnetoresistance of current-perpendicular-to-plane spin valves with Co2FeSi Heusler alloy

We fabricated current-perpendicular-to-plane spin valves (SV) using Co2FeSi and Co2(Cr0.1Fe0.9)Si Heusler alloys as ferromagnetic layers and a Ag spacer. The SV with Co2(Cr0.1Fe0.9)Si showed relatively large magnetoresistance (MR) ratio of 11.9 % and the resistance change-area product (ΔRA) of 6.3 mΩ μm2 at room temperature as compared to the MR ratio of 9.4% and the ΔRA value of 4.1 mΩ μm2 for the SV using Co2FeSi. This indicates that the spin polarization of Co2FeSi is enhanced by the substitution of Cr for Fe as suggested by a previous point contact Andreev reflection measurements. Considering the high Curie temperature of 993 K, the Co2(Cr0.1Fe0.9)Si alloy could be promising material for spin polarized electron source.