Enhanced magnetization drift velocity and current polarization in (CoFe)1−xGex alloys

A spin-wave Doppler technique is used to measure the drift velocity of the magnetization in current-carrying (CoFe)1−xGex alloys. For a current density of 1011 A/m2, we obtain a large enhancement of drift velocity with increased Ge concentration from 3.1±0.2 m/s for CoFe to 8.2±0.6 m/s for (CoFe)0.7Ge0.3. Interpretation of these values yields current polarization increasing from 0.84±0.04 to 0.95±0.05 as the Ge doping increases. While both spin-dependent conductivities decrease with increasing Ge concentration, the maximum in polarization is associated with a stronger relative change in the minority spin conductivity.