Deciphering M–T diagram of shape memory Heusler alloys: reentrance, plateau and beyond

We present our recent results on temperature behaviour of magnetization observed in Heusler alloys. Three regions can be distinguished in the M–T diagram: (I) low temperature martensitic phase (with the Curie temperature  K), (II) intermediate mixed phase (with the critical temperature  K) exhibiting a reentrant like behavior (between and ) and (III) high temperature austenitic phase (with the Curie temperature  K) exhibiting a rather wide plateau region (between and ). By arguing that powerful structural transformations, causing drastic modifications of the domain structure in alloys, would also trigger strong fluctuations of the order parameters throughout the entire M–T diagram, we were able to successfully fit all the data by incorporating Gaussian fluctuations (both above and below the above three critical temperatures) into the Ginzburg–Landau scenario.