Electron Concentration Dependence of Phase Transition and Magnetic Properties in NiMnGa Alloys

The phase transition, Curie temperature and magnetic properties of NiMnGa alloys represented by S1, S2, S3, and S4 in different atomic percentage were investigated from TG/DTA and PPMS measurements. It was found that the electron concentration (e/a) ratio of S1 and S4 as well as S2 and S3 are equal to each other. The transformation temperatures and magnetization values are similar for these alloys having the same e/a. Results show that room temperature magnetization depends on valence electron concentration of alloys and saturation of alloys increases with the decrease of e/a ratio. The measured coercivity values for all alloys were above 125 Oe and they had a long saturation field, i.e., above 10000 Oe, by exhibiting, the characteristics of hard magnetic materials.