NiMnGa polycrystalline magnetically activated shape memory alloys

We report on the structural characteristics, magnetic properties and magnetically induced deformations obtained on as produced and annealed samples of bulk polycrystalline NiMnGa alloys. Extensive structural, magnetic and magnetomechanical characteristic are presented. A peak cyclic strain of the order of 1.2 10(-4), connected to the presence of martensite twins, is found when a magnetic field is applied. Annealing produces positive effects on the austenite to martensite transition, on the overall magnetic properties but does not produce a larger strain, These results are discussed with reference to previously published data.