The role of stationarity in magnetic crackling noise

We discuss the effect of stationarity on the avalanche statistics of Barkhausen noise signals. We perform experimental measurements on an Fe85B15 amorphous ribbon and compare the avalanche distributions measured around the coercive field, where the signal is stationary, with those sampled through the entire hysteresis loop. In the first case, we recover scaling exponents (tau similar to 1.38, alpha similar to 1.65) close to the commonly observed values for other amorphous materials, while in the second the exponents are significantly larger (tau similar to 1.7, alpha similar to 2.2). We provide a quantitative explanation of the experimental results through a model for the depinning of a ferromagnetic domain wall. The present analysis sheds light on the unusually high values for the Barkhausen noise exponents measured by Spasojevic et al.