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

TL;DR

This paper investigates the temperature-dependent magnetization behavior in Ni_47Mn_39In_14 Heusler alloys, revealing distinct phases and reentrant phenomena, modeled through Gaussian fluctuations within a Ginzburg-Landau framework.

Contribution

It introduces a comprehensive Ginzburg-Landau model incorporating Gaussian fluctuations to explain complex magnetic phase transitions in Heusler alloys.

Findings

Identification of three distinct magnetic phases with specific critical temperatures.

Observation of reentrant behavior in the intermediate phase.

Successful fitting of experimental data using the fluctuation-inclusive model.

Abstract

We present our recent results on temperature behaviour of magnetization observed in Ni_47Mn_39In_14 Heusler alloys. Three regions can be distinguished in the M-T diagram: (I) low temperature martensitic phase (with the Curie temperature T_CM = 140 K), (II) intermediate mixed phase (with the critical temperature T_MS = 230 K) exhibiting a reentrant like behavior (between T_CM and T_MS) and (III) high temperature austenitic phase (with the Curie temperature T_CA = 320 K) exhibiting a rather wide plateau region (between T_MS and T_CA). 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.