Chapter Four - Magnetic-Field-Induced Effects in Martensitic Heusler-Based Magnetic Shape Memory Alloys

Abstract

Publisher Summary The discovery of the ferromagnetic (FM) Heusler alloy Cu 2 MnAl, in the beginning of the twentieth century, made considerable impact in the field of magnetism. Although Cu 2 MnAl contained no FM element, it had a very high Curie temperature in excess of 600 K. Features related to the magnetostructural interplay in Heusler alloys are observed in the phonon and magnetization properties. This chapter discusses Heusler-based magnetic shape memory alloys. The complex behavior displayed by these materials is mainly a consequence of the strong coupling between magnetism and structure, which is driven by the martensitic transition. Magnetic shape memory properties are the best known functionalities shown by this class of materials. They refer to the ability of these alloys to show strong response in shape, strain, and dimensions to applied magnetic fields. The magnetic field triggers the changes of shape caused by either inducing the structural transition or rearranging the martensite variants. The first observation of the magnetic-field-controlled shape memory effect was made in Ni 2 MnGa. It is suggested that the mechanism giving rise to the large magnetostriction in Ni 2 MnGa consisted of a twin-related variant reorientation through field-induced twin-boundary motion.