Alternative harmonic detection approach for quantitative determination of spin and orbital torques

TL;DR

This paper introduces an alternative harmonic Hall voltage technique in out-of-plane geometry for precise quantification of spin-orbit torques, validated experimentally and analytically, with implications for orbital current research.

Contribution

It develops and validates a new harmonic Hall detection method for SOT measurement, enabling complete thermoelectric effect characterization in systems with in-plane magnetic anisotropy.

Findings

Demonstrates a two-fold increase in damping-like torques with copper oxide interfaces.

Validates the analytical derivation of the out-of-plane harmonic Hall detection geometry.

Shows the method's ability to accurately quantify SOT and thermoelectric effects.

Abstract

In this study, the spin-orbit torque (SOT) in light metal oxide systems is investigated using an experimental approach based on harmonic Hall voltage techniques in out-of-plane (OOP) angular geometry for samples with in-plane magnetic anisotropy. In parallel, an analytical derivation of this alternative OOP harmonic Hall detection geometry has been developed, followed by experimental validation to extract SOT effective fields. In addition, to accurately quantifying SOT, this method allows complete characterization of thermoelectric effects, opening promising avenues for accurate SOT characterization in related systems. In particular, this study corroborates the critical role of naturally oxidized copper interfaced with metallic Cu in the generation of orbital current in Co(2)|Pt(4)|CuOx(3), demonstrating a two-fold increase in damping-like torques compared to a reference sample with an oxidized Al capping layer. These findings offer promising directions for future research on the application aspect of non-equilibrium orbital angular momentum.