Quantitative scaling of magnetic avalanches

TL;DR

This study compares experimental Barkhausen noise data from magnetic materials with theoretical avalanche predictions, confirming the theory's accuracy for certain conditions and identifying effects of eddy currents.

Contribution

First quantitative validation of avalanche theory against Barkhausen noise experiments across different magnetic materials and sample geometries.

Findings

Long-range and short-range samples fit theory well without eddy currents.

Short-range samples provide the first reliable test beyond mean-field theory.

Thick samples show deviations indicating eddy current effects.

Abstract

We provide the first quantitative comparison between Barkhausen-noise experiments and recent predictions from the theory of avalanches for pinned interfaces, both in and beyond mean-field. We study different classes of soft magnetic materials: polycrystals and amorphous samples, characterized by long-range and short-range elasticity, respectively; both for thick and thin samples, i.e. with and without eddy currents. The temporal avalanche shape at fixed size, and observables related to the joint distribution of sizes and durations are analyzed in detail. Both long-range and short-range samples with no eddy currents are fitted extremely well by the theoretical predictions. In particular, the short-range samples provide the first reliable test of the theory beyond mean field. The thick samples show systematic deviations from the scaling theory, providing unambiguous signatures for the presence of eddy currents.