Pathways of structural and magnetic transitions in ferromagnetic shape memory alloys

TL;DR

This study investigates the magnetoelastic coupling in ferromagnetic shape memory alloys, revealing the sequence of magnetic and structural transitions during heating and cooling using a novel high-speed electronic method.

Contribution

It introduces magnetic transition spectra, a new technique to analyze domain dynamics, and clarifies the sequence of magnetic and structural transitions in NiMnGa and FePd alloys.

Findings

Structural transition precedes magnetic transition during cooling.

Magnetic transition precedes structural transition during heating.

New high-speed method effectively captures temperature-dependent domain dynamics.

Abstract

A fundamental question in the study of ferromagnetic shap ememory alloys is the nature of magnetoelastic coupling and the extent it drives the structural transformation. This question also holds the key to developing new and optimized alloys that combine high strains at low switching field. In the present study it is shown that the reconfiguration of the micromagnetic structure is enslaved to and follows the martensitic transformation in these alloys using the NiMnGa and FePd alloy systems. This is determined by developing a new, high speed electronic method to study the temperature dependence of domain dynamics, called magnetic transition spectra. The sequence of magnetic and structural transition was found to be as follows. For cooling, structural transition followed by magnetic transition and for heating, magnetic transition followed by structural transition.