Effect of Disorder in the Frustrated Ising FCC Antiferromagnet: Phase Diagram and Stretched Exponential Relaxation

TL;DR

This study investigates how introducing ferromagnetic bonds affects phase transitions in a frustrated Ising FCC antiferromagnet, revealing rapid suppression of order and the emergence of a spin glass phase, with detailed relaxation dynamics.

Contribution

It provides the first comprehensive phase diagram for the FCC antiferromagnet with bond disorder and analyzes the relaxation behavior near the spin-glass transition.

Findings

First-order transition disappears at p~0.01

Antiferromagnetic order vanishes around p~0.05

System transitions from antiferromagnetic to spin glass to ferromagnetic phases

Abstract

We study the phase transition in a face-centered-cubic antiferromagnet with Ising spins as a function of the concentration $p$ of ferromagnetic bonds randomly introduced into the system. Such a model describes the spin-glass phase at strong bond disorder. Using the standard Monte Carlo simulation and the powerful Wang-Landau flat-histogram method, we carry out in this work intensive simulations over the whole range of $p$. We show that the first-order transition disappears with a tiny amount of ferromagnetic bonds, namely $p\sim 0.01$, in agreement with theories and simulations on other 3D models. The antiferromagnetic long-range order is also destroyed with a very small $p$ ($\simeq 5%$). With increasing $p$, the system changes into a spin glass and then to a ferromagnetic phase when $p>0.65$. The phase diagram in the space ($T_c,p$) shows an asymmetry, unlike the case of the $\pm J$ Ising spin glass on the simple cubic lattice. We calculate the relaxation time around the spin-glass transition temperature and we show that the spin autocorrelation follows a stretched exponential relaxation law where the factor $b$ is equal to $\simeq 1/3$ at the transition as suggested by the percolation-based theory. This value is in agreement with experiments performed on various spin glasses and with Monte Carlo simulations on different SG models.