Universality and scaling in the Barkhausen noise

Since its discovery by H. Barkhausen in 1919, the jerky motion of domain walls in bulk soft magnetic materials has represented a unique tool to study the microscopic processes responsible for magnetic hysteresis. Previously, the description of this complex motion has been purely phenomenological, without any precise connection with the magnetization processes involved or the material microstructure. Recently, using different approaches proper of statistical mechanics, new microscopic models have been introduced, allowing to link the observed statistical properties of the noise to material parameters. In particular, Barkhausen jumps are found to exhibit universal properties, with size and duration distributions showing scaling. Remarkably, the properties of the noise of different materials can be grouped into two universality classes, depending only on the strength of long range interactions. Here we review recent studies, with a particular emphasis on the still existing discrepancies between the available experimental data and the theoretical predictions. We also show that this approach is useful to investigate the general properties of magnetic hysteresis, and the dynamics of domain walls in thin films, an important technological open problem strongly debated in the recent literature.