Full angular dependence of the spin Hall and ordinary magnetoresistance in epitaxial antiferromagnetic NiO(001)/Pt thin films

TL;DR

This study measures the three-dimensional angular dependence of spin Hall magnetoresistance in epitaxial NiO(001)/Pt thin films, revealing insights into antiferromagnetic spin transport and domain behavior without ferromagnetic elements.

Contribution

It provides the first detailed 3D angular dependence of SMR in NiO/Pt bilayers and models the domain redistribution effects influencing the SMR signal.

Findings

SMR observed between 1 and 3 T without saturation up to 11 T

Reversible field-induced redistribution of antiferromagnetic domains explains angular dependence

Estimated spin mixing conductance exceeds 2×10^{14} Ω^{-1} m^{-2}

Abstract

We report the observation of the three-dimensional angular dependence of the spin Hall magnetoresistance (SMR) in a bilayer of the epitaxial antiferromagnetic insulator NiO(001) and the heavy metal Pt, without any ferromagnetic element. The detected angular-dependent longitudinal and transverse magnetoresistances are measured by rotating the sample in magnetic fields up to 11 T, along three orthogonal planes (xy-, yz- and xz-rotation planes, where the z-axis is orthogonal to the sample plane). The total magnetoresistance has contributions arising from both the SMR and ordinary magnetoresistance. The onset of the SMR signal occurs between 1 and 3 T and no saturation is visible up to 11 T. The three-dimensional angular dependence of the SMR can be explained by a model considering the reversible field-induced redistribution of magnetostrictive antiferromagnetic S- and T-domains in the NiO(001), stemming from the competition between the Zeeman energy and the elastic clamping effect of the non-magnetic MgO substrate. From the observed SMR ratio, we estimate the spin mixing conductance at the NiO/Pt interface to be greater than $2\times10^{14}$ ${\Omega}^{-1}$ $m^{-2}$. Our results demonstrate the possibility to electrically detect the N\'eel vector direction in stable NiO(001) thin films, for rotations in the xy- and xz- planes. Moreover, we show that a careful subtraction of the ordinary magnetoresistance contribution is crucial to correctly estimate the amplitude of the SMR.