Driving and detecting ferromagnetic resonance in insulators with the spin Hall effect

TL;DR

This paper demonstrates the generation and detection of spin-torque ferromagnetic resonance in Pt/YIG bilayers using the spin Hall effect, without charge current passing through the insulator, revealing complex spin interactions.

Contribution

It introduces a method to generate and detect ferromagnetic resonance in insulators via the spin Hall effect, highlighting the role of the imaginary component of spin mixing conductance.

Findings

Detection of dc voltage linked to YIG resonance

Identification of spin Hall magnetoresistance and spin pumping effects

Necessity of imaginary spin mixing conductance component for out-of-plane fields

Abstract

We demonstrate the generation and detection of spin-torque ferromagnetic resonance in Pt/YIG bilayers. A unique attribute of this system is that the spin Hall effect lies at the heart of both the generation and detection processes and no charge current is passing through the insulating magnetic layer. When the YIG undergoes resonance, a dc voltage is detected longitudinally along the Pt that can be described by two components. One is the mixing of the spin Hall magnetoresistance with the microwave current. The other results from spin pumping into the Pt being converted to a dc current through the inverse spin Hall effect. The voltage is measured with applied magnetic field directions that range in-plane to nearly perpendicular. We find that for magnetic fields that are mostly out-of-plane, an imaginary component of the spin mixing conductance is required to model our data.