Negative spin Hall magnetoresistance in antiferromagnetic Cr2O3/Ta bilayer at low temperature region

TL;DR

This study reveals a temperature-dependent sign change in spin Hall magnetoresistance in Cr2O3/Ta bilayers, linked to competing surface and bulk antiferromagnetic effects, with implications for interface magnetism.

Contribution

It demonstrates the temperature-driven sign reversal of SMR in Cr2O3/Ta bilayers and links it to interface magnetic phenomena, providing new insights into antiferromagnetic spin transport.

Findings

SMR sign changes from positive to negative between 300 K and 50 K.

The SMR ratio and Hall curve slopes correlate with interface magnetism.

Estimated spin mixing conductance is comparable to other known structures.

Abstract

We investigate the observation of negative spin Hall magnetoresistance (SMR) in antiferromagnetic Cr2O3/Ta bilayers at low temperature. The sign of the SMR signals is changed from positive to negative monotonously from 300 K to 50 K. The change of the signs for SMR is related with the competitions between the surface ferromagnetism and bulky antiferromagnetic of Cr2O3. The surface magnetizations of Cr2O3 (0001) is considered to be dominated at higher temperature, while the bulky antiferromagnetics gets to be robust with decreasing of temperature. The slopes of the abnormal Hall curves coincide with the signs of SMR, confirming variational interface magnetism of Cr2O3 at different temperature. From the observed SMR ratio under 3 T, the spin mixing conductance at Cr2O3/Ta interface is estimated to be 1.12*10^14 (ohm^-1*m^-2), which is comparable to that of YIG/Pt structures and our early results of Cr2O3/W. (Appl. Phys. Lett. 110, 262401 (2017))