Anisotropic magnetoresistance in antiferromagnetic Sr2IrO4

TL;DR

This study investigates the anisotropic magnetoresistance in antiferromagnetic Sr2IrO4 using point-contact measurements, revealing large AMR effects linked to spin-orbit coupling and magnetic order, with potential implications for spintronics.

Contribution

First detailed local probe of AMR in Sr2IrO4 showing large AMR effects and magnetic field-induced symmetry transition, advancing understanding of spin-orbit interactions in antiferromagnets.

Findings

Negative magnetoresistance up to 28% at modest fields

Crossover from four-fold to two-fold symmetry in AMR

Large AMR compared to 3d transition metal oxides

Abstract

We report point-contact measurements of anisotropic magnetoresistance (AMR) in a single crystal of antiferromagnetic (AFM) Mott insulator Sr2IrO4. The point-contact technique is used here as a local probe of magnetotransport properties on the nanoscale. The measurements at liquid nitrogen temperature revealed negative magnetoresistances (MRs) (up to 28%) for modest magnetic fields (250 mT) applied within the IrO2 a-b plane and electric currents flowing perpendicular to the plane. The angular dependence of MR shows a crossover from four-fold to two-fold symmetry in response to an increasing magnetic field with angular variations in resistance from 1-14%. We tentatively attribute the four-fold symmetry to the crystalline component of AMR and the field-induced transition to the effects of applied field on the canting of AFM-coupled moments in Sr2IrO4. The observed AMR is very large compared to the crystalline AMRs in 3d transition metal alloys/oxides (0.1-0.5%) and can be associated with the large spin-orbit interactions in this 5d oxide while the transition provides evidence of correlations between electronic transport, magnetic order and orbital states. The finding of this work opens an entirely new avenue to not only gain a new insight into physics associated with spin-orbit coupling but also better harness the power of spintronics in a more technically favorable fashion.