Quantification of spin-charge interconversion in highly resistive sputtered Bi${}_x$Se${}_{1-x}$ with non-local spin valves

Abstract

The development of spin-orbitronic devices, such as magneto-electric 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 Bi${}_x$Se${}_{1-x}$. Although there are several techniques to quantify spin-charge interconversion, to date reported values for sputtered Bi${}_x$Se${}_{1-x}$ 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, non-local spin valves are used to inject pure spin currents into Bi${}_x$Se${}_{1-x}$, 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 Bi${}_x$Se${}_{1-x}$, 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.

12 pages, 4 figures, 1 table, and Supplemental Material

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