# Random-field-induced disordering mechanism in a disordered ferromagnet: Between the Imry-Ma and the standard disordering mechanism

## TL;DR

This paper identifies a new disordering mechanism in disordered ferromagnets driven by finite-size glassy domains at moderate random fields, expanding understanding beyond traditional Imry-Ma and standard mechanisms.

## Contribution

It demonstrates that a third disordering mechanism exists in ferromagnets with competing interactions, applicable to a broad class of disordered magnetic systems.

## Key findings

- Disordered ferromagnets can be disordered by finite-size glassy domains at moderate random fields.
- The new mechanism is supported by large-scale Monte Carlo simulations and zero-temperature numerical methods.
- The transition may be first order based on finite-size scaling analysis.

## Abstract

Random fields disorder Ising ferromagnets by aligning single spins in the direction of the random field in three space dimensions, or by flipping large ferromagnetic domains at dimensions two and below. While the former requires random fields of typical magnitude similar to the interaction strength, the latter Imry-Ma mechanism only requires infinitesimal random fields. Recently, it has been shown that for dilute anisotropic dipolar systems a third mechanism exists, where the ferromagnetic phase is disordered by finite-size glassy domains at a random field of finite magnitude that is considerably smaller than the typical interaction strength. Using large-scale Monte Carlo simulations and zero-temperature numerical approaches, we show that this mechanism applies to disordered ferromagnets with competing short-range ferromagnetic and antiferromagnetic interactions, suggesting its generality in ferromagnetic systems with competing interactions and an underlying spin-glass phase. A finite-size-scaling analysis of the magnetization distribution suggests that the transition might be first order.