Critical behavior and universality properties of uniaxial ferromagnetic thin films in the presence of random magnetic fields

TL;DR

This study investigates the critical behavior and universality in uniaxial ferromagnetic thin films affected by random magnetic fields, revealing tricritical points and universal properties unaffected by disorder.

Contribution

It demonstrates that disorder does not alter the universality class of ferromagnetic thin films and identifies conditions for tricritical behavior and critical surface-bulk exchange ratios.

Findings

Presence of tricritical points with bimodal disorder

Critical surface to bulk exchange ratio is unaffected by disorder

Universality class remains unchanged despite random magnetic fields

Abstract

Critical phenomena in uniaxial ferromagnetic thin films in the presence of random magnetic fields have been studied within the framework of effective field theory. When the type of the random field distribution is bimodal, the system exhibits tricritical behavior. Furthermore, the critical value of surface to bulk ratio of exchange interactions at which the transition temperature becomes independent of film thickness is insensitive to the presence of disorder whether the distribution is bimodal or trimodal. Regarding the universality properties, neither $p$, nor $h$ variations in the system can affect the value of the shift exponent $\lambda$. In this regard, it can be concluded that pure ferromagnetic thin films are in the same universality class with those under the influence of random discrete magnetic fields.