Quantification of spin-charge interconversion in highly resistive sputtered BixSe1-x with nonlocal spin valves

The development of spin-orbitronic devices, such as magnetoelectric spin-orbit logic devices, calls for materials with a high resistivity and a high spin-charge interconversion efficiency. One of the most promising candidates in this regard is sputtered BixSe1-x. Although there are several techniques to quantify spin-charge interconversion, reported values to date for sputtered BixSe1-x have often been overestimated due to spurious effects related to local currents combined with a lack of understanding of the effect of the interfaces and the use of approximations for unknown parameters, such as the spin diffusion length. In the present study, nonlocal spin valves are used to inject pure spin currents into BixSe1-x, allowing us to directly obtain its spin diffusion length as well as its spin Hall angle, from 10 K up to 300 K. These values, which are more accurate than those previously reported in sputtered BixSe1-x, evidence that the efficiency of this material is not exceptional. Indeed, the figure of merit for spin-charge interconversion, given by the product of these two parameters, is slightly under 1 nm. Our work demonstrates the importance of considering all material parameters and interfaces when quantifying the spin transport properties of materials with strong spin-orbit coupling.