Giant magnetic field induced strain in ferromagnetic shape memory alloys and its condition

Abstract

Ferromagnetic shape memory alloys are a kind of multiferroic material, in which a ferroelastic domain (variant in the martensite phase) and a magnetic domain are closely correlated. One interesting phenomenon due to this correlation is the rearrangement of variants by a magnetic field, which causes a large magnetic field induced strain of several percent. Typical alloys exhibiting such behaviour are disordered Fe–31˙2Pd, Fe₃Pt (degree of order ∼0˙8) and Ni₂MnGa. In the present paper, the martensitic transformation behaviour and the magnetic field induced strain have been examined for these three alloys. In addition, considering the results obtained, the condition for realising the large magnetic field induced strain will be derived and its propriety will be confirmed quantitatively.