Low-temperature transformation and electronic structure of (Ni1-xCox)2MnGa

Low-temperature structural transformation of (Ni1-xCox)2MnGa was investigated experimentally and theoretically. Magnetization measurement as a function of temperature in the low magnetic field revealed that the transformation temperature T1 disappeared for x>=0.2. The band calculation predicted that the stabilization of austenite L21 phase occurred for x>0.3, which was in rough agreement with the experimental result. Furthermore, the instability of austenite phase was discussed from the viewpoint of Hume-Rothery regime and the prediction was in good agreement with the results. It was concluded that the Galanakis curve was a good prediction for half-metal Heusler alloy and a new Heusler alloy was proposed for 1.0>x>=0.7