FCC Fe2NiSi prepared by mechanical alloying and stabilization effect of L21B disorder on BCC Heusler structure

Abstract Fe 2 NiSi FCC phase has been prepared by ball-milling successfully, which is different from the BCC Heusler phase prepared by arc-melting in previous literatures. The FCC Fe 2 NiSi is a ferromagnet with a lattice constant of 3.58 A. The phase stability of the FCC and BCC Fe 2 NiSi has been compared by first-principles calculations. It has been found that the FCC structure has a lower total energy compared with the highly-ordered Heusler structures XA and L2 1 , that is the reason why the FCC phase can be prepared by ball-milling. However, the Fe (A)–Ni (C) disorder in the BCC XA structure can lower its total energy further and make it smaller than the FCC phase. So the most stable structure in Fe 2 NiSi is L2 1 B, as has been observed in the arc-melting sample. This can be explained from their DOS structures. The calculated total moments for the FCC and BCC phases agree with their M s at 5 K quite well.