Temperature dependence of magnetization drift velocity and current polarization in Ni80Fe20 by spin-wave Doppler measurements

A spin-wave Doppler technique is used to measure the temperature dependence of both the magnetization drift velocity, which represents the magnitude of adiabatic spin-transfer torque, and the current polarization in current-carrying Ni80Fe20 wires. For current densities of 10(11) A/m(2), we obtain magnetization drift velocities decreasing from 4.8 +/- 0.3 to 4.1 +/- 0.1 m/s over a temperature range from 80 to 340 K. Interpretation of velocity values yields current polarization dropping from 0.75 +/- 0.05 to 0.58 +/- 0.02 over the same temperature range. Analysis indicates different temperature dependences for spin-up and spin-down conductivities, suggesting a strong impurity scattering of spin-down electrons.