Magnetic properties and magnetostructural phase transitions in Ni2+xMn1-xGa shape memory alloys

TL;DR

This study investigates the magnetic properties and phase transitions in Ni2+xMn1-xGa shape memory alloys, revealing how composition affects transition temperatures and magnetic moments in ferromagnetic and paramagnetic states.

Contribution

It provides a systematic analysis of magnetostructural phase transitions and magnetic moments in Ni2+xMn1-xGa alloys, incorporating experimental data and theoretical estimations.

Findings

Martensitic transition temperature shifts weakly with composition.

Magnetic moments and Curie temperatures were estimated for different phases.

Transition temperatures align with Clapeyron-Clausius predictions.

Abstract

A systematic study of magnetic properties of Ni2+xMn1-xGa (0 \le x \le 0.19) Heusler alloys undergoing structural martensite-austenite transformations while in ferromagnetic state has been performed. From measurements of spontaneous magnetization, Ms(T), jumps \Delta M at structural phase transitions were determined. Virtual Curie temperatures of the martensite were estimated from the comparison of magnetization in martensitic and austenitic phases. Both saturation magnetic moments in ferromagnetic state and effective magnetic moments in paramagnetic state of Mn and Ni atoms were estimated and the influence of delocalization effects on magnetism in these alloys was discussed. The experimental results obtained show that the shift of martensitic transition temperature depends weakly on composition. The values of this shift are in good correspondence with Clapeyron-Clausius formalism taking into account the experimental data on latent heat at martensite-austenite transformations.