Universal properties of magnetization dynamics in polycrystalline ferromagnetic films

TL;DR

This study reveals that polycrystalline ferromagnetic films exhibit universal three-dimensional magnetization dynamics governed by long-range dipolar interactions, regardless of thickness, challenging the assumption of two-dimensional behavior in thin films.

Contribution

It demonstrates that the scaling behavior of Barkhausen noise in ferromagnetic films aligns with a mean-field three-dimensional model across various thicknesses.

Findings

Samples belong to a single universality class with specific exponents.

Films exhibit 3D magnetization dynamics governed by dipolar interactions.

Two-dimensional behavior is not universal for all film thicknesses.

Abstract

We investigate the scaling behavior in the statistical properties of Barkhausen noise in ferromagnetic films. We apply the statistical treatment usually employed for bulk materials in experimental Barkhausen noise time series measured with the traditional inductive technique in polycrystalline ferromagnetic films having different thickness from 100 up to 1000 nm, and investigate the scaling exponents. Based on this procedure, we can group the samples in a single universality class, characterized by exponents \tau \sim 1.5, \alpha \sim 2.0, and 1/\sigma \nu z \sim \vartheta \sim 2.0. We interpret these results in terms of theoretical models and provide experimental evidence that a well-known mean-field model for the dynamics of a ferromagnetic domain wall in three-dimensional ferromagnets can be extended for films. We identify that the films present an universal three-dimensional magnetization dynamics, governed by long-range dipolar interactions, even at the smallest thicknesses, indicating that the two-dimensional magnetic behavior commonly verified for films cannot be generalized for all thickness ranges.