Geometry dependent crossover of Barkhausen statistics in iron thin films

We report the crossover of Barkhausen noise statistics upon a change in the measurement geometry. The behaviour is akin to the angle dependent critical to sub-critical crossover of avalanche statistics as present in avalanche models with random anisotropy directions. The samples studied were 15–25 nm thin films of iron, grown on (001) GaAs by pulsed laser ablation. Use of planar Hall effect as a probe for the magnetic state facilitated this work, which would be impractical to do in a MOKE setup. We compare our data with simulations of a random anisotropy Ising model, and demonstrate striking similarity between experimental and simulated avalanche size distributions. Further, through micromagnetic simulations, we conclude that crystallite misorientations were the origin of domain wall pinning in our system leading to Barkhausen noise.