Spin Torque Ferromagnetic Resonance Induced by the Spin Hall Effect

TL;DR

This paper demonstrates how the spin Hall effect in a Pt/NiFe bilayer can induce ferromagnetic resonance, enabling quantitative analysis of spin currents and the spin Hall angle through electrical measurements.

Contribution

It introduces a method to excite and measure ferromagnetic resonance via the spin Hall effect in a bilayer, providing a way to quantify spin currents and the spin Hall angle.

Findings

Spin Hall effect induces FMR in adjacent ferromagnetic film.

The ratio of signals separates spin Hall and Oersted contributions.

Quantitative determination of spin current and spin Hall angle achieved.

Abstract

We demonstrate that the spin Hall effect in a thin film with strong spin-orbit scattering can excite magnetic precession in an adjacent ferromagnetic film. The flow of alternating current through a Pt/NiFe bilayer generates an oscillating transverse spin current in the Pt, and the resultant transfer of spin angular momentum to the NiFe induces ferromagnetic resonance (FMR) dynamics. The Oersted field from the current also generates an FMR signal but with a different symmetry. The ratio of these two signals allows a quantitative determination of the spin current and the spin Hall angle.