Driving-induced crossover in the avalanche criticality of martensitic transitions

An experimental study of the statistical distribution of acoustic emission avalanches in martensitic transitions is presented. The critical exponents characterizing the power-law distributions of avalanches are measured as a function of cycling under soft-driving (stress-driving) and hard-driving (strain-driving) procedures. Results provide experimental support for a recent theory based on a spin model that predicts a crossover from classical criticality in the soft-driving case to self-organized criticality in the hard-driving case.