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

Mark W. Keller; Katy S. Gerace; Monika Arora; Erna Krisztina Delczeg-Czirjak; Justin M. Shaw; T. J. Silva

doi:10.1103/PhysRevB.99.214411

paper

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

arXiv:1903.00910 · doi:10.1103/PhysRevB.99.214411

Abstract

We report a large spin Hall effect in the 3 $d$ transition metal alloy Ni $_{x}$ Cu $_{1 - x}$ for $x \in {0.3, 0.75}$ , 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 $θ_{SH} \approx 1$ , spin diffusion length $λ_{s}$ , spin mixing conductance $G_{↑↓}$ , and damping $α_{SML}$ 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

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Interface enhancement of Gilbert damping from first-principles

Near-Unity Spin Hall Ratio in Nix​Cu1−x​ Alloys

Abstract

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