Barkhausen Noise from Precessional Domain Wall Motion

The jerky dynamics of domain walls driven by applied magnetic fields in disordered ferromagnets---the Barkhausen effect---is a paradigmatic example of crackling noise. We study Barkhausen noise in disordered $\mathrm{Pt}/\mathrm{Co}/\mathrm{Pt}$ thin films due to precessional motion of domain walls using full micromagnetic simulations, allowing for a detailed description of the domain wall internal structure. In this regime the domain walls contain topological defects known as Bloch lines which repeatedly nucleate, propagate, and annihilate within the domain wall during the Barkhausen jumps. In addition to bursts of domain wall propagation, the in-plane Bloch line dynamics within the domain wall exhibits crackling noise and constitutes the majority of the overall spin rotation activity.