Finite-Temperature Properties of Three-Dimensional Classical Chiral Helimagnets

TL;DR

This study investigates the finite-temperature behavior of three-dimensional chiral helimagnets using mean-field theory and Monte Carlo simulations, providing insights into magnetic properties and parameter estimation for specific materials.

Contribution

It combines mean-field and Monte Carlo methods to analyze chiral helimagnets, improving quantitative accuracy by including spin correlations and clarifying the applicability of continuum models.

Findings

Magnetization curves align qualitatively with experiments.

Including spin correlations enhances quantitative results.

Estimated interaction parameters for CrNb3S6 support a layered spin coupling picture.

Abstract

A three-dimensional chiral helimagnet is analyzed using a mean-field (MF) analysis and a classical Monte Carlo (MC) simulation at finite temperatures. We consider a Hamiltonian containing Heisenberg exchange and uni-axial Dzyaloshinskii-Moriya interactions on a simple cubic lattice. Magnetization curves calculated by the MF theory are qualitatively consistent with those observed in experiments. A comparison between lattice and continuum models clarifies the region where the continuum approximation can be applied. By combining the MF theory with the classical MC method, it is also clarified that results are quantitatively much improved by including spin correlations in the layer perpendicular to the helical axis. On the basis of our simple model, interaction parameters in $CrNb_3S_6$ are estimated. These values of exchange interactions justify a physical picture that the spins are strongly coupled in the two-dimensional layer and are weakly interacted with those in the helical chain.