Theory of bound magnetic polarons in cubic and uniaxial antiferromagnets

TL;DR

This paper develops a theory of bound magnetic polarons in anisotropic antiferromagnetic semiconductors, explaining experimental magnetization phenomena and predicting hysteresis in uniaxial cases, with implications for understanding remanent magnetization and Hall effects.

Contribution

The paper introduces a comprehensive theory of bound magnetic polarons in anisotropic antiferromagnets, addressing experimental observations and predicting hysteresis in uniaxial systems.

Findings

Quantitative explanation of excess magnetization in EuTe

Prediction of magnetization hysteresis in uniaxial antiferromagnets

Alignment of theoretical remanent magnetization with experimental data for MnTe

Abstract

Motivated by a recent debate about the origin of remanent magnetization and the corresponding anomalous Hall effect in antiferromagnets and altermagnets, a theory of bound magnetic polarons (BMPs) in anisotropic antiferromagnetic semiconductors is developed. The theory describes quantitatively the experimentally observed magnitude of excess magnetization and its dependence on the magnetic field in cubic antiferromagnetic EuTe. In contrast to the cubic case, our theory predicts the presence of magnetization hysteresis below N\'eel temperature in antiferromagnets with uniaxial anisotropy. We show, employing material parameters implied by experimental and ab initio results, that the magnitudes of remanent magnetization and the coercive field are in accord with recent experimental observations for altermagnetic hexagonal MnTe. While the altermagnets have an intrinsic contribution to the remanent magnetization and the anomalous Hall effect, our theory explains the origin of an extrinsic contribution. Our findings address, therefore, a question about the relative contribution to the remanent magnetization of bound magnetic polarons and weak ferromagnetism driven by the antisymmetric exchange interaction, the latter weakened by the formation of antiferromagnetic domains. Furthermore, we provide the theory of BMP spontaneous spin splitting, which can be probed optically.