Nonequilibrium phase transitions and tricriticality in a three-dimensional lattice system with random-field competing kinetics

TL;DR

This paper investigates a nonequilibrium 3D Ising model with competing spin-flip mechanisms, revealing first-order and continuous phase transitions, and identifying a nonequilibrium tricritical point through Monte Carlo simulations.

Contribution

It introduces a novel nonequilibrium kinetic model with competing dynamics and characterizes its phase transition behavior and critical exponents.

Findings

First-order transitions at low temperatures and high disorder.

Existence of a nonequilibrium tricritical point.

Continuous phase transitions with estimated critical exponents.

Abstract

We study a nonequilibrium Ising model that stochastically evolves under the simultaneous operation of several spin-flip mechanisms. In other words, the local magnetic fields change sign randomly with time due to competing kinetics. This dynamics models a fast and random diffusion of disorder that takes place in dilute metallic alloys when magnetic ions diffuse. We performe Monte Carlo simulations on cubic lattices up to L=60. The system exhibits ferromagnetic and paramagnetic steady states. Our results predict first-order transitions at low temperatures and large disorder strengths, which correspond to the existence of a nonequilibrium tricritical point at finite temperature. By means of standard finite-size scaling equations, we estimate the critical exponents in the low-field region, for which our simulations uphold continuous phase transitions.