Spin-Hall magnetoresistance in a low-dimensional magnetic insulator

TL;DR

This study reveals unusual spin Hall magnetoresistance behavior in a Pt film on a strained LaCoO3 insulator, indicating a low-dimensional magnetic surface state and providing a new method to probe quantum surface magnetism.

Contribution

It demonstrates a novel magnetic surface state in LaCoO3 and relates SMR behavior to microscopic interfacial magnetic properties, expanding understanding of surface magnetism.

Findings

SMR amplitude increases linearly with magnetic field beyond saturation.

SMR remains measurable above the Curie temperature.

No hysteresis observed in the SMR field dependence.

Abstract

We observe an unusual behavior of the spin Hall magnetoresistance (SMR) measured in a Pt ultra-thin film deposited on a ferromagnetic insulator, which is a tensile-strained LaCoO3 (LCO) thin film with the Curie temperature Tc=85K. The SMR displays a strong magnetic-field dependence below Tc, with the SMR amplitude continuing to increase (linearly) with increasing the field far beyond the saturation value of the ferromagnet. The SMR amplitude decreases gradually with raising the temperature across Tc and remains measurable even above Tc. Moreover, no hysteresis is observed in the field dependence of the SMR. These results indicate that a novel low-dimensional magnetic system forms on the surface of LCO and that the Pt/LCO interface decouples magnetically from the rest of the LCO thin film. To explain the experiment, we revisit the derivation of the SMR corrections and relate the spin-mixing conductances to the microscopic quantities describing the magnetism at the interface. Our results can be used as a technique to probe quantum magnetism on the surface of a magnetic insulator.