Temperature dependence of magnetoresistive output of pseudo spin valves with Co2Fe(Al1−<i>x</i>Si<i>x</i>) Heusler alloys and a Ag spacer

Abstract

We investigated the temperature dependence of magnetoresistive (MR) outputs of current-perpendicular-to-plane pseudo spin valves with Co2FeAl1−xSix (0 ≤ x ≤ 1) Heusler alloy ferromagnetic layers and a Ag spacer layer to optimize x. The MR ratios at room temperature do not show x dependence, while the MR ratios measured at 5 K showed strong x dependence; the largest resistance change-area product ΔRA = 21 mΩ·μm2 was obtained for x = 1 and ΔRA decreased with decreasing x. The results apparently contradicts with the theoretical prediction that the highest spin polarization is attained for x = 0.5. The discrepancy is due to the structural origin that the L21 order is obtained only in the Co2FeSi alloy film.