We studied various Heusler alloy compositions for the ferromagnetic layers of current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) spin-valves (SVs) to obtain large MR outputs for the read sensor applications. The exchange biased SV with Co2 Fe(Al0.5 Si0.5 ) alloy showed a resistance change-area product (Δ RA) of 6 mΩ μm 2 and an MR ratio of 21% at room temperature when the Co2 Fe(Al0.5 Si0.5 ) layer was well-B2-ordered by a high temperature annealing at 500°C. The critical bias current density for the spin torque effect on the reduction of ΔRA was ∼ 3 × 10 7 A/cm2. Based on the high spin polarization directly measured by the point contact Andreev reflection method, Co2 (Cr 0.1 Fe0.9 )Si, Co2 Mn(Ga0.5 Sn 0.5 ), and Co2 Fe(Ge0.5 Ga0.5 ) alloy thin films were investigated for CPP-GMR SVs. Among them, the Co 2Fe(Ge0.5Ga0.5) alloy showed a high CPP-GMR ratio in the pseudo SVs exceeding 40% at RT and 120% at 10 K.
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