MAGNETOCALORIC EFFECT IN Ni-Mn-BASED FERROMAGNETIC SHAPE-MEMORY ALLOYS

摘要

In this paper we review the magnetocaloric properties of Ni-Mn-based Heusler alloys in the vicinity of their martensitic transition and its relation to their magnetic shape-memory and superelastic behaviour. We show that this striking magnetomechanical behaviour is possible thanks to the existence of a strong interplay between structure and magnetism in this class of materials. This interplay enables a magnetic field re-arrangement of twin-related martensitic variants as well as the possibility of magnetically inducing the martensitic transition. These two effects are respectively controlled by the magnetocrystalline anisotropy of the martensitic phase and by the difference of magnetic moments between martensitic and parent phases. We show that the magnetocaloric properties in these Heusler materials are determined from contributions associated with these two effects and discuss the requirements for the occurrence of the inverse magnetocaloric effect.