Novel disordering mechanism in ferromagnetic systems with competing interactions

TL;DR

This paper uncovers a new disordering mechanism in three-dimensional ferromagnetic systems with competing interactions influenced by a random field, driven by an underlying spin-glass phase, which explains experimental observations in specific materials.

Contribution

It introduces a novel disordering mechanism in ferromagnetic systems with competing interactions, highlighting the role of an underlying spin-glass phase beyond the traditional Imry-Ma argument.

Findings

Disorder occurs at smaller random fields than typical interaction strengths.

The mechanism explains the temperature dependence of critical behavior in LiHo_xY_{1-x}F_4.

Results align with experimental observations of susceptibility broadening.

Abstract

Ferromagnetic Ising systems with competing interactions are considered in the presence of a random field. We find that in three space dimensions the ferromagnetic phase is disordered by a random field which is considerably smaller than the typical interaction strength between the spins. This is the result of a novel disordering mechanism triggered by an underlying spin-glass phase. Calculations for the specific case of the long-range dipolar LiHo_xY_{1-x}F_4 compound suggest that the above mechanism is responsible for the peculiar dependence of the critical temperature on the strength of the random field and the broadening of the susceptibility peaks as temperature is decreased, as found in recent experiments by Silevitch et al. [Nature (London) 448, 567 (2007)]. Our results thus emphasize the need to go beyond the standard Imry-Ma argument when studying general random-field systems.