Mastering disorder in a first-order transition by ion irradiation

The effect of ion irradiation on MnAs single crystalline thin films is studied. The role of elastic collisions between ions and atoms of the material is singled out as the main process responsible for modifying the properties of the material. Thermal hysteresis suppression, and the loss of sharpness of the magnetostructural phase transition, are studied as a function of different irradiation conditions. While the latter is shown to be associated with ion-induced disorder at the scale of the transition correlation length, the former is related to the coupling between disorder and the large-scale elastic field associated with the phase coexistence pattern.