  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 Pt/Co/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.
