Giant anisotropic magnetoresistance with dual-four-fold symmetry in CaMnO3/CaIrO3 heterostructures

TL;DR

This paper reports a giant dual-four-fold symmetric anisotropic magnetoresistance (AMR) of 70% in CaMnO3/CaIrO3 heterostructures, significantly larger than previous systems, driven by lattice effects and spin-flop transitions.

Contribution

It introduces a novel mechanism for large AMR in 3d-5d heterostructures through combined charge-transfer, interlayer coupling, and spin-flop transitions.

Findings

Achieved 70% AMR signal, two orders larger than prior systems.

Identified dual mechanisms: biaxial anisotropy and spin-flop transition.

Demonstrated potential for sensing and memory applications in antiferromagnetic spintronics.

Abstract

The realization of four-fold anisotropic magnetoresistance (AMR) in novel 3d-5d heterostructures has boosted major efforts in antiferromagnetic spintronics. However, despite the potential of incorporating strong spin-orbit coupling, only small AMR signals have been detected thus far, prompting a search for new mechanisms to enhance the signal. In this study on CaMnO3/CaIrO3 heterostructures, we report a unique dual-four-fold symmetric 70% AMR; a signal two orders of magnitude larger than previously observed in similar systems. We find that one order is enhanced by tuning a large biaxial anisotropy through octahedral tilts of similar sense in the constituent layers, while the second order is triggered by a spin-flop transition in a nearly Mott-type phase. Dynamics between these two phenomena as evidenced by the step-like AMR and a superimposed biaxial-anisotropy-induced AMR capture a subtle interplay of pseudospin coupling with the lattice and external magnetic field. Our study shows that a combination of charge-transfer, interlayer coupling, and a spin-flop transition can yield a giant AMR relevant for sensing and antiferromagnetic memory applications.