Magnetic Field-Induced Strain in Ferromagnetic Shape Memory Alloys Fe-31.2Pd, Fe3Pt, and Ni2MnGa

Abstract

Ferromagnetic shape memory alloys are a kind of multiferroic materials, in which a ferroelastic domain (variant in the martensite phase) and a magnetic domain are closely correlated. One interesting phenomenon caused by this correlation is the rearrangement of martensite variants by magnetic field, which is associated with a large magnetic field-induced strain of several percent. Typical alloys exhibiting such behavior are disordered Fe-31.2Pd (at.%), Fe3Pt (degree of order∼0.8), and Ni2MnGa. In this chapter, we show martensitic transformation behavior and the magnetic field-induced strain in these three alloys. Then, we will derive the condition for realizing a large magnetic field-induced strain in ferromagnetic shape memory alloys. In addition, the origin of a weak first-order martensitic transformation in Fe3Pt is discussed from its electronic structure.