The propagation of a phase front during a thermally induced martensitic transition is discontinuous due to pinning at various defects, an effect which results in acoustic emission. Here we analyze the consequences of an applied compressive stress exemplarily on a ${\text{Ni}}_{50.4}{\text{Mn}}_{27.9}{\text{Ga}}_{21.7}$ single crystal. Our experiments show that the distribution of the energies of the acoustic emission events follows a power law for more than three decades. This indicates that the transition exhibits avalanche criticality. The exponent characterizing the distribution of energies depends on the applied stress, and decreases from $1.9\pm 0.1$ at zero stress to $1.5\pm 0.2$ at stress above $3\mathrm{MPa}$. This decrease could be attributed to the reduced multiplicity of variants possible under uniaxial compression.

• Received 3 September 2012

DOI:https://doi.org/10.1103/PhysRevB.86.214101