Ferromagnetic resonance phase imaging in spin Hall multilayers

TL;DR

This paper uses time-resolved anomalous Nernst effect microscopy to image the magnetic precession phase in spin Hall multilayers, revealing spatial phase variations that impact the measurement of spin Hall angles.

Contribution

It introduces a method to image FMR phase in spin Hall multilayers and analyzes how spatial phase variations affect spin Hall angle measurements.

Findings

Spatial variation of FMR phase observed across the channel

Phase variation introduces systematic correction in spin Hall angle estimation

Method provides detailed insight into the driving field orientation

Abstract

We experimentally image the magnetic precession phase of patterned spin Hall multilayer samples to study the rf driving field vector using time-resolved anomalous Nernst effect (TRANE) microscopy. Our ferromagnetic resonance (FMR) measurements quantify the phase and amplitude for both the magnetic precession and the electric current, which allows us to establish the total driving field orientation and the strength of spin Hall effect. In a channel of uniform width, we observe spatial variation of the FMR phase laterally across the channel. We interpret our findings in the context of electrical measurement using the spin-transfer torque ferromagnetic resonance technique and show that observed phase variation introduces a systematic correction into the spin Hall angle if spatial phase and amplitude variations are not taken into account.