Earthquake-like dynamics in ultrathin magnetic film

TL;DR

This paper investigates the intermittent, earthquake-like creep dynamics of magnetic domain walls in ultrathin films, revealing scale-free avalanche behavior consistent with the quenched KPZ universality class.

Contribution

It uncovers the scale-free avalanche statistics of domain wall reorganizations, linking magnetic creep dynamics to earthquake-like phenomena and the quenched KPZ universality class.

Findings

Creep dynamics are highly intermittent and correlated.

Large reorganizations follow scale-free statistics.

Reorganizations are consistent with the quenched KPZ universality class.

Abstract

We study the motion of a domain wall on an ultrathin magnetic film using the magneto-optical Kerr effect (MOKE). At tiny magnetic fields, the wall creeps only via thermal activation over the pinning centers present in the sample. Our results show that this creep dynamics is highly intermittent and correlated. A localized instability triggers a cascade, akin to aftershocks following a large earthquake, where the pinned wall undergoes large reorganizations in a compact active region for a few seconds. Surprisingly, the size and shape of these reorganizations display the same scale-free statistics of the depinning avalanches in agreement with the quenched Kardar-Parisi-Zhang universality class.