Four-fold Anisotropic Magnetoresistance in Antiferromagnetic Epitaxial Thin Films of MnPt$_{x}$Pd$_{1-x}$

TL;DR

This study investigates anisotropic magnetoresistance in epitaxial thin films of MnPt$_{x}$Pd$_{1-x}$ antiferromagnets, revealing thickness-dependent behaviors and the role of interfacial interactions in magnetotransport properties.

Contribution

It reports the first observation of AMR in MnPt$_{x}$Pd$_{1-x}$ thin films and elucidates the origins of crystalline and non-crystalline AMR components.

Findings

Thicker films show non-crystalline two-fold AMR dominated by domain reconfiguration.

Thinner films exhibit crystalline four-fold AMR with an uncompensated magnetic moment.

Interfacial interactions increase the density of states at the Fermi level, stabilizing the moment.

Abstract

Antiferromagnets are emerging as promising alternatives to ferromagnets in spintronics applications. A key feature of antiferromagnets is their anisotropic magnetoresistance (AMR), which has the potential to serve as a sensitive marker for the antiferromagnetic order parameter. However, the underlying origins of this behavior remains poorly understood, particularly, in thin film geometries. In this study, we report the observation of AMR in epitaxial thin films of the collinear L1$_{0}$ antiferromagnet MnPt$_{x}$Pd$_{1-x}$. In the thicker films, AMR is dominated by a non-crystalline two-fold component, which emerges from domain reconfiguration and spin canting under applied magnetic field. As the film thickness is reduced, however, a crystalline four-fold component emerges, accompanied by the appearance of uncompensated magnetic moment, which strongly modifies the magnetotransport properties in the thinner films. We demonstrate that interfacial interactions lead to a large density of states (DOS) at the Fermi level. This enhanced DOS, combined with disorder in the thinner films, stabilizes the uncompensated moment and results in a four-fold modulation of the DOS as the Neel vector rotates, explaining the observed AMR behavior.