Magneto-optical study of metamagnetic transitions in the antiferromagnetic phase of $\alpha$-RuCl$_3$

TL;DR

This study uses magneto-optical techniques to explore metamagnetic transitions and magnetic anisotropy in the antiferromagnetic phase of $ ext{α-RuCl}_3$, revealing complex spin reorientations and intermediate phases.

Contribution

It provides new insights into the field-induced magnetic transitions and anisotropic interactions in $ ext{α-RuCl}_3$ using magneto-optical effects, clarifying the nature of metamagnetic behavior.

Findings

Identification of spin-flop transition at ~1.6 T

Detection of a field-induced intermediate phase

Quantification of bond-anisotropic interactions

Abstract

$\alpha$-RuCl$_3$ is a promising candidate material to realize the so far elusive quantum spin liquid ground state. However, at low temperatures, the coexistence of different exchange interactions couple the effective pseudospins into an antiferromagnetically zigzag (ZZ) ordered state. The low-field evolution of spin structure is still a matter of debate and the magnetic anisotropy within the honeycomb planes is an open and challenging question. Here, we investigate the evolution of the ZZ order parameter by second-order magneto-optical effects, the magnetic linear dichroism and magnetic linear birefringence. Our results clarify the presence and nature of metamagnetic transitions in the ZZ phase of $\alpha$-RuCl$_3$. Our experimental observations show the presence of initial magnetic domain repopulation followed by a spin-flop transition for small in-plane applied magnetic fields ($\approx$ 1.6 T) along specific crystallographic directions. In addition, using a magneto-optical approach, we detected the recently reported emergence of a field-induced intermediate phase before suppressing the ZZ order. Our results disclose the details of various angle-dependent in-plane metamagnetic transitions quantifying the bond-anisotropic interactions present in $\alpha$-RuCl$_3$