DecipheringM–Tdiagram of shape memory Heusler alloys: reentrance, plateau and beyond

Abstract

We present our recent results on temperature behavior of magnetization observed in N i47M n39In14 Heusler alloys. Three regions can be distinguished in the M −T diagram: (I) low temperature martensitic phase (with the Curie temperature TCM = 140K), (II) intermediate mixed phase (with the critical temperature TMS = 230K) exhibiting a reentrant like behavior (between TCM and TMS), and (III) high temperature austenitic phase (with the Curie temperature TCA = 320K) exhibiting a rather wide plateau region (between TMS and TCA). 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.