Near-Unity Spin Hall Ratio in Ni${}_x$Cu${}_{1-x}$ Alloys

Abstract

We report a large spin Hall effect in the 3$d$ transition metal alloy Ni${}_x$Cu${}_{1-x}$ for $x\in \left\{0.3,0.75\right\}$, detected via the ferromagnetic resonance of a Permalloy (Py = Ni${}_{80}$Fe${}_{20}$) film deposited in a bilayer with the alloy. A thickness series at $x$ = 0.6, for which the alloy is paramagnetic at room temperature, allows us to determine the spin Hall ratio ${\theta }_{\mathrm{SH}}\approx 1$, spin diffusion length ${\lambda }_{\mathrm{s}}$, spin mixing conductance $G_{\uparrow \downarrow }$, and damping ${\alpha }_{\mathrm{SML}}$ due to spin memory loss . We compare our results with similar experiments on Py/Pt bilayers measured using the same method. Ab initio band structure calculations with disorder and spin-orbit coupling suggest an intrinsic spin Hall effect in Ni${}_x$Cu${}_{1-x}$ alloys, although the experiments here cannot distinguish between extrinsic and intrinsic mechanisms.

New ab initio calculations of Ni-Cu alloy band structure added; new author; new fig in main text and new appendix describing calculations

References in corpus (1)

• Interface enhancement of Gilbert damping from first-principles