Effective Model for Rare-earth Kitaev Materials and its Classical Monte Carlo Simulation

TL;DR

This paper proposes an effective spin Hamiltonian for rare-earth Kitaev materials, uses classical Monte Carlo simulations to explore their phase diagram, and analyzes magnetic properties and phase transitions relevant to experimental observations.

Contribution

The work introduces a new effective spin model consistent with crystal symmetry and applies classical Monte Carlo methods to study its magnetic phases and thermodynamic properties.

Findings

Multiple magnetic long-range orders identified at low temperatures.

Thermodynamic properties like susceptibility and heat capacity are calculated and show consistent transition temperatures.

Magnetic susceptibility varies with direction, with the stripe phase showing isotropic susceptibility.

Abstract

Recently, the family of rare-earth chalcohalides were proposed as candidate compounds to realize the Kitaev spin liquid (KSL). In the present work, we firstly propose an effective spin Hamiltonian consistents with the symmetry group of the crystal structure. Then we apply classical Monte Carlo simulations to preliminarily study the model and establish a phase diagram. When approaching to the low temperature limit, several magnetic long range orders are observed, including the stripe, the zigzag, the antiferromagnetic (AFM), the ferromagnetic (FM), the incommensurate spiral (IS), the Multi-$\pmb {Q}$ and the 120{\deg}. We further calculate the thermodynamic properties of the system, such as the temperature dependence of the magnetic susceptibility and the heat capacity. The ordering transition temperatures reflected in the two quantities agree with each other. For most interaction regions, the system is magnetically more susceptible in the $ab$-plane than in the $c$-direction. The stripe phase is special, where the susceptibility is fairly isotropic in the whole temperature region. These features provide useful information to understand the magnetic properties of related materials.