Low-field magnetization processes of hexagonal easy-plane altermagnet $\alpha$-MnTe

TL;DR

This study investigates the magnetic properties of hexagonal $ ext{MnTe}$ crystals, revealing complex domain behaviors and anisotropies explained by a micromagnetic model including higher-order exchange interactions.

Contribution

It introduces a phenomenological micromagnetic model that accounts for complex magnetic responses and anisotropies in $ ext{MnTe}$, highlighting the role of metastable domains and irreversible processes.

Findings

Antiferromagnetic transition at $T_N \\approx 307$ K.

Complex magnetic responses linked to domain structures.

Model captures uniaxial and unidirectional anisotropies.

Abstract

Single crystals of $\alpha$-MnTe were synthesized by chemical vapor transport using iodine as the transport reagent. Structural characterization by powder x-ray diffraction confirmed the hexagonal structure (space group P6$_{3}$/mmc). Magnetization $M(T)$ and specific heat $C_p(T)$ measurements revealed an antiferromagnetic phase transition at $T_N \approx307$ K. The magnetic entropy derived from the $C_p(T)$ data is consistent with the $S = 5/2$ spin state of Mn$^{2+}$ ions. Angle- and field-dependent magnetization measurements indicate complex magnetic responses associated with domains, and show an anomaly around 1 T. These features are analyzed using a phenomenological micromagnetic model that includes higher-order anisotropic exchange interactions coupling the weak ferromagnetic component and the antiferromagnetic order parameter. The model captures the generic behavior of magnetic states and demonstrates that the observed uniaxial and unidirectional anisotropies arise from metastable domain configurations and irreversible magnetization processes.