The role of stationarity in magnetic crackling noise

We discuss the effect of the stationarity on the avalanche statistics of Barkhuasen noise signals. We perform experimental measurements on a Fe${}_{85}$B${}_{15}$ 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 the scaling exponents commonly observed in other amorphous materials ($\tau =1.3$, $\alpha =1.5$). while in the second the exponents are significantly larger ($\tau =1.7$, $\alpha =2.2$). We provide a quantitative explanation of the experimental results through a model for the depinning of a ferromagnetic domain wall. The present analysis shed light on the unusually high values for the Barkhausen noise exponents measured by Spasojevic et al. [Phys. Rev. E 54 2531 (1996)].