# Spin structure and spin Hall magnetoresistance of epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO$_3$

## TL;DR

This study investigates the spin structure and spin Hall magnetoresistance in epitaxial thin films of the non-collinear antiferromagnet SmFeO$_3$, revealing unique magnetic properties and temperature-dependent SMR behavior.

## Contribution

It provides the first detailed imaging of the AFM spin structure and demonstrates the distinct SMR characteristics in SmFeO$_3$ compared to collinear AFMs.

## Key findings

- SmFeO$_3$ spins align in the film plane.
- SmFeO$_3$/Ta bilayers show positive SMR, unlike collinear AFMs.
- SMR amplitude increases with magnetic field and temperature.

## Abstract

We report a combined study of imaging the antiferromagnetic (AFM) spin structure and measuring the spin Hall magnetoresistance (SMR) in epitaxial thin films of the insulating non-collinear antiferromagnet SmFeO$_3$. X-ray magnetic linear dichroism photoemission electron microscopy measurements reveal that the AFM spins of the SmFeO$_3$(110) align in the plane of the film. Angularly dependent magnetoresistance measurements show that SmFeO$_3$/Ta bilayers exhibit a positive SMR, in contrast to the negative SMR expected in previously studied collinear AFMs. The SMR amplitude increases linearly with increasing external magnetic field at higher magnetic field, suggesting that field-induced canting of the AFM spins plays an important role. In contrast, around the coercive field, no detectable SMR signal is observed, indicating that SMR of AFM and canting magnetization components cancel out. Below 50~K, the SMR amplitude increases sizably by a factor of two as compared to room temperature, which likely correlates with the long-range ordering of the Sm ions. Our results show that the SMR is a sensitive technique for non-equilibrium spin system of non-collinear AFM systems.