J. Phys. IV France 112 (2003) 907
DOI: 10.1051/jp4:20031028

Displacive phase transformations and magnetic properties in Ni-Mn-Ga ferromagnetic shape memory alloys

K. Tsuchiya¹, A. Tsutsumi¹, H. Nakayama¹, S. Ishida², H. Ohtsuka³ and M. Umemoto<sup>1

1</sup>  Toyohashi University of Technology, Department Production Systems Engineering, Toyohashi, Aichi 441-8580, Japan
²  Kagoshima University, Department Physics, Faculty of Science, Kagoshima 890-0065, Japan
³  National Institute for Materials Science, Material Engineering Laboratory, Tsukuba, Ibaraki 305-0003, Japan

Abstract
Composition dependence of displacive phase transformation behavior has been studied on Ni-Mn-Ga ferromagnetic shape memory alloys. A good correlation was found between the valence electron density ( e/a) and martensitic transformation temperature, intermediated phase transformation temperature and the Curie temperature, as well as the values of magnetization. Crystal structure of martensite also changes with e/a. Transformation from the parent phase to the intermediate phase and then to the martensite phase were observed in-situ by TFM. The intermediate phase was characterized by the satellite spots at 1/6g ₂₂₀ positions irrespective of the structure of martensite obtained by the further cooling. Composition dependence of the martensitic transformation temperature was compared with the prediction of electronic band structure calculation.

© EDP Sciences 2003