Beyond power laws: Universality in the average avalanche shape

TL;DR

This paper measures the average shape of Barkhausen noise avalanches in thin films, demonstrating consistency with mean-field theories and providing insights into universality beyond simple power laws.

Contribution

It introduces a novel experimental approach to measure avalanche shapes and compares results with mean-field theory, accounting for demagnetizing fields and field ramp-rate effects.

Findings

Experimental avalanche shapes are approximately symmetric.

Scaling functions evolve predictably with experimental conditions.

Quantitative agreement between theory and experiment is achieved.

Abstract

We report the measurement of multivariable scaling functions for the temporal average shape of Barkhausen noise avalanches, and show that they are consistent with the predictions of simple mean-field theories. We bypass the confounding factors of time-retarded interactions (eddy currents) by measuring thin permal- loy films, and bypass thresholding effects and amplifier distortions by applying Wiener deconvolution. We find experimental shapes that are approximately symmetric, and track the evolution of the scaling function. We solve a mean- field theory for the magnetization dynamics and calculate the form of the scaling function in the presence of a demagnetizing field and a finite field ramp-rate, yielding quantitative agreement with the experiment.