Cobalt-based Heusler alloys for spin-injection devices

Co2MnGa and Co2MnIn are ideal half-metallic materials for spin-injection in nanostructured semiconductor devices. Magneto-optical Kerr effect and electrical transport measurements demonstrate that although these alloys can be integrated with semiconductor devices, the metallic phase dominates over the intrinsic, minority spin phase of the alloy. Co2MnGa: GaAs(001) has a weak uniaxial magnetic anisotropy with the easy axis along the [0, -1,1] in-plane direction. Co2MnIn : GaAs(001) has no in-plane anisotropy. Metallic behavior is concomitant with ferromagnetic behavior, as the anisotropic magnetoresistance tends to zero at the same film thickness (similar to100 Angstrom) that the residual resistivity ratio extrapolates to 1. Co2MnIn has an AMR of similar to0.5%, however, an AMR as large as 6% is observed in Co2MnGa at 300 K. This demonstrates the potential for nanostructured devices, although the first 100 Angstrom of alloy growth will determine the spin- injection efficiency.