Field-induced intermediate ordered phase and anisotropic interlayer interactions in $\alpha$-RuCl$_3$

TL;DR

This study reveals an intermediate magnetic phase in $ ext{RuCl}_3$ induced by an in-plane magnetic field, characterized by a six-layer periodicity and driven by anisotropic interlayer interactions, highlighting their crucial role in the material's magnetic behavior.

Contribution

The paper identifies and characterizes a new intermediate ordered phase in $ ext{RuCl}_3$ and emphasizes the significance of anisotropic interlayer couplings in its magnetic properties.

Findings

Discovery of an intermediate-field ordered phase with six-layer periodicity.

Neutron diffraction confirms the magnetic structure of the intermediate phase.

Theoretical modeling shows interlayer anisotropic couplings explain the intermediate phase.

Abstract

In $\alpha$-RuCl$_3$, an external magnetic field applied within the honeycomb plane can induce a transition from a magnetically ordered state to a disordered state that is potentially related to the Kitaev quantum spin liquid. In zero field, single crystals with minimal stacking faults display a low-temperature state with in-plane zigzag antiferromagnetic order and a three-layer periodicity in the direction perpendicular to the honeycomb planes. Here, we present angle-dependent magnetization, ac susceptibility, and thermal transport data that demonstrate the presence of an additional intermediate-field ordered state at fields below the transition to the disordered phase. Neutron diffraction results show that the magnetic structure in this phase is characterized by a six-layer periodicity in the direction perpendicular to the honeycomb planes. Theoretically, the intermediate ordered phase can be accounted for by including spin-anisotropic couplings between the layers in a three-dimensional spin model. Together, this demonstrates the importance of interlayer exchange interactions in $\alpha$-RuCl$_3$.