Spin-dependent transport in uranium

Abstract

Given the challenges in experimental studies of uranium, the heaviest naturally occurring metal, we present first-principles calculation for the spin-dependent transport. Showing the largest atomic spin-orbit coupling we explore the ability of various crystal phases to maximise the charge to spin conversion using a full relativistic Korringa-Kohn-Rostoker Greens function method. The transport theory is based on a semi classical description where intrinsic and extrinsic, skew scattering, contributions can be separated easily. In addition to the various crystal phases we analyse the effect of substitutional impurities for γ, hcp, as well as the α-phase. We predict a very high, 10 4 (Ωcm) −1 , spin Hall conductivity for the meta-stable hcp-U phase, a giant value 5 times larger than for the conventional spin Hall material Pt. We estimated an efficiency of charge-to-spin current conversion of up to 30%. The spin diffusion length, a crucial parameter in any application, is predicted to be in the range from 3 − 6.5nm, compatible with other charge-to-spin conversion materials. Relating our work to the sparse experimental results, our calculations suggest a γ phase in the thin film rather than the experimentally expected α phase.

Electronic Impurity Scattering Induced Spin Accumulation in Metallic Thin Films

“…This strong Cu-induced accumulation differs notably from Ref. [61] that demonstrated a vanishing spin Hall angle for Cu doped bcc bulk U. The reason for that discrepancy is the incorporation of intrinsic effects in the normalized spin accumulation as calculated here while the calculations in Ref.…”

“…The reason for that discrepancy is the incorporation of intrinsic effects in the normalized spin accumulation as calculated here while the calculations in Ref. [61] were restricted to the extrinsic skew-scattering mechanism as captured by the scattering-in term.…”

Spin accumulation in metallic thin films induced by electronic impurity scattering

“…This strong Cuinduced accumulation differs notably from Ref. [61], which demonstrated a vanishing spin Hall angle for Cu-doped bcc bulk U. The reason for this discrepancy is the restriction to the skew-scattering mechanism in Ref.…”

“…The reason for this discrepancy is the restriction to the skew-scattering mechanism in Ref. [61], while here we incorporate contributions arising from the spatial inversion symmetry breaking induced by the impurity scattering.…”

Magnetic anisotropy in Fe/U and Ni/U bilayers

“…Density Functional Theory calculations were carried out using a fully relativistic Korringa-Kohn-Rostoker Greens function method 26 extended to include calculations for the Bloch spectral function 27 Further details of the calculations for the uranium crystal can be found in Ref. 28.…”