Ferromagnetic shape memory alloys Ni_2±x±yMn _1±xGa_1±y

Magnetically driven shape memory alloys, among them Ni _2±x±yMn_1±xGa_1±y, represent a novel type of material which allow magnetic fields to influence their shape and dimensions in a martensitic state. The basic approach to employ the intelligent properties of these compounds is associated with the rearrangement of martensitic variants by the magnetic field. To realize this possibility, the magnetic anisotropy of the martensitic phase should be large enough to overcome the potential barriers for the motion of the martensite domain boundaries. Huge strains at room temperatures were reported under the competing stress of about 1 MPa and a magnetic field of about 1 T.