Radiation-induced transformations in Heusler alloys ion-irradiated to high doses

We have studied the structures and properties of Heusler alloys of the Cu-Mn-Al and Ni-Mn-Ga systems irradiated by 40-keV Ar⁺ ions. It is established that magnetic properties of ion-irradiated samples exhibit strong variation in a narrow range of target temperatures. This variation is accompanied by significant changes in the X-ray diffraction pattern. With allowance for the results of our previous investigations, it is suggested that (i) the observed changes in the diffraction patterns are caused by the formation of nanoclusters in the crystal lattice, the symmetry of which is different from that of the initial matrix structure, and (ii) the appearance of these clusters accounts for the observed change in the magnetic properties of Heusler alloys.