Critical Dynamics of Anisotropic Antiferromagnets in an External Field

TL;DR

This study numerically explores the non-equilibrium critical dynamics of three-dimensional anisotropic antiferromagnets under an external magnetic field, revealing critical exponents and dynamic behaviors at different critical lines and a bicritical point.

Contribution

It introduces a hybrid computational approach to analyze aging and dynamic critical exponents in anisotropic antiferromagnets near criticality and bicritical points.

Findings

Identified critical initial slip, autocorrelation, and aging exponents for model C.

Measured dynamic critical exponents for the order parameter and conserved field.

Analyzed system size dependence of spin wave frequencies near criticality.

Abstract

We numerically investigate the non-equilibrium critical dynamics in three-dimensional anisotropic antiferromagnets in the presence of an external magnetic field. The phase diagram of this system exhibits two critical lines that meet at a bicritical point. The non-conserved components of the staggered magnetization order parameter couple dynamically to the conserved component of the magnetization density along the direction of the external field. Employing a hybrid computational algorithm that combines reversible spin precession with relaxational Monte Carlo updates, we study the aging scaling dynamics for the model C critical line, identifying the critical initial slip, autocorrelation, and aging exponents for both the order parameter and conserved field, thus also verifying the dynamic critical exponent. We further probe the model F critical line by investigating the system size dependence of the characteristic spin wave frequencies near criticality, and measure the dynamic critical exponents for the order parameter including its aging scaling at the bicritical point.