Electrical spin injection and detection in semimetallic Bi and Bi-Pb films

Abstract

The spin injection technique is extended to semimetal bismuth samples in a lateral spin valve geometry. We study spin injection, diffusion, and detection in a material system where a small change in sample stoichiometry results in a large change in the electronic and spin dependent transport properties of the nonmagnetic material. Measurements of magnetoresistance, using a magnetic field applied in the sample plane, as well as the Hanle effect, using a field applied perpendicular to the sample plane, are reported. We demonstrate two remarkable results: (i) a spin diffusion length of $230\text{ }\ensuremath{\mu}\text{m}$ $(T=2\text{ }\text{K})$ in a BiPb sample with temperature dependent resistivity, $\ensuremath{\rho}(T)$, which decreases with decreasing $T$ is the longest known value in a thin film; (ii) the interfacial spin polarization is 10% in BiPb samples with decreasing $\ensuremath{\rho}(T)$ and an order of magnitude smaller (0.8%) in Bi samples where $\ensuremath{\rho}(T)$ increases with decreasing $T$.