Tunable scaling behaviour observed in Barkhausen criticality of a ferromagnetic film

Abstract

A ferromagnetic material shows a sequence of discrete and jerky domain jumps, known as the Barkhausen avalanche1,2, in the presence of an external magnetic field. Studies of Barkhausen avalanches reveal power-law scaling behaviour that suggests an underlying criticality3,4,5,6,7,8, as observed in a wide variety of systems such as superconductor vortices9, microfractures10, earthquakes11, lung inflations12, mass extinctions13, financial markets14 and charge-density waves15. The most interesting unsolved fundamental question is whether the universality in the scaling exponent holds regardless of the material and its detailed microstructure. Here we show that the scaling behaviour of Barkhausen criticality in a given ferromagnetic film is experimentally tunable by varying the temperature (not dimensionality). We observe for the first time that the scaling behaviour in the Barkhausen criticality of a given system crosses over between two universality classes when the relative contributions from the dipolar interaction and domain-wall energies are altered by an experimental parameter.