Theoretical and experimental study of the phase formation for Ti2YAl and Ti2Y′Ga (Y = Co, Fe; Y′ = Cr, Fe)

Abstract The site preference and phase formation of Ti 2 YAl and Ti 2 Y′Ga (Y = Co, Fe; Y′ = Cr, Fe) have been investigated by theoretical calculation and experimental study. It has been found that Ti 2 CoAl and Ti 2 FeAl are stable in Hg 2 CuTi-type structure, while Ti 2 CrGa and Ti 2 FeGa compounds are most likely to form Cu 2 MnAl-type structure. These results indicate that not all full-Heusler alloys follow the site preference rule, especially when the transition metals are low-valent metals. The differences of band structures and magnetic properties between Hg 2 CuTi-type and Cu 2 MnAl-type structures for the above compounds are also studied by first-principles calculation. It has been predicted that Ti 2 FeAl, Ti 2 FeGa and Ti 2 CoAl are half-metallic compounds in Hg 2 CuTi-type structure, while their half-metallic properties are completely destroyed as they formed Cu 2 MnAl-type structure.