Effect of antiferromagnetic exchange interactions on the Glauber dynamics of one-dimensional Ising models

TL;DR

This paper investigates how antiferromagnetic interactions influence the Glauber dynamics of 1D Ising models, revealing resonant behavior and universality class differences in relaxation dynamics.

Contribution

It introduces a detailed analysis of antiferromagnetic effects on Glauber dynamics in 1D Ising models, including ferrimagnetic resonance and universality class distinctions.

Findings

Resonant stochastic behavior occurs in ferrimagnetic chains.

ANNNI chain dynamics differ from unfrustrated Ising models.

Calculated dynamic critical exponent suggests a different universality class.

Abstract

We study the effect of antiferromagnetic interactions on the single spin-flip Glauber dynamics of two different one-dimensional (1D) Ising models with spin $\pm 1$. The first model is an Ising chain with antiferromagnetic exchange interaction limited to nearest neighbors and subject to an oscillating magnetic field. The system of master equations describing the time evolution of sublattice magnetizations can easily be solved within a linear field approximation and a long time limit. Resonant behavior of the magnetization as a function of temperature (stochastic resonance) is found, at low frequency, only when spins on opposite sublattices are uncompensated owing to different gyromagnetic factors (i.e., in the presence of a ferrimagnetic short range order). The second model is the axial next-nearest neighbor Ising (ANNNI) chain, where an antiferromagnetic exchange between next-nearest neighbors (nnn) is assumed to compete with a nearest-neighbor (nn) exchange interaction of either sign. The long time response of the model to a weak, oscillating magnetic field is investigated in the framework of a decoupling approximation for three-spin correlation functions, which is required to close the system of master equations. The calculation, within such an approximate theoretical scheme, of the dynamic critical exponent z, defined as ${1/\tau} \approx ({1/ {\xi}})^z$ (where \tau is the longest relaxation time and \xi is the correlation length of the chain), suggests that the T=0 single spin-flip Glauber dynamics of the ANNNI chain is in a different universality class than that of the unfrustrated Ising chain.