Field-induced strain under load in Ni–Mn–Ga magnetic shape memory materials

Abstract

Single-crystal Ni2MnGa shows a nearly 0.2% strain under a magnetic field of 8 kOe at −8 °C. Polycrystalline samples have been prepared near stoichiometry to study the composition dependence of the magnetic and elastic properties. A narrow band of compositions has been found having a range of Curie and martensitic transformation temperatures, Tc and T0, extending to above room temperature. The compressive stress–strain characteristics in variable transverse field were studied in samples selected to have T0 just below room temperature. Stress-induced martensite was observed as expected and the magnetic field was applied under fixed load for various stresses. A transverse field of 3200 Oe caused the sample to strain under load doing work that increased up to 1.3 J/kg with increasing volume fraction of stress-induced martensite.