Spin Injection and Accumulation in the Planar NiFe–InSb–NiFe and NiFe–Cu–NiFe Spin Valves

Abstract

Spin injection and accumulation have been studied for NiFe–InSb–NiFe and NiFe–Cu–NiFe planar spin valves with direct injection current I in nonlocal (NLSV) and local (LSV) measurement configurations at temperature 8–300 K. The value of the generated voltage U and the character of the dependence U(I) drastically changed for currents I greater some critical value I_c due to thermoelectric effects. For NLSV configuration and currents I<I_c the value of U is of 2–3 order of magnitude higher for NiFe–InSb–NiFe (U ≈ 1–3 mV at 300 K) structures in comparison with NiFe–Cu–NiFe (U ≈ 4–20 µV at 8 K). For LSV geometry electrical detection of spin current was observed only for NiFe–Cu–NiFe structure, where for I<I_c the magnetoresistance (MR) effect of the order 0.5% was detected. For currents I of 1.5–2% higher than I_c the MR of the order of 10–30% was observed for both NLSV and LSV configurations for studied structures.