Nitrogen ordering and ferromagnetic properties of epsilon-Fe3N1=x (0.10 <=x <= 0.39) and epsilon-Fe-3(N0.80C0.20)(1.38)

The epsilon -phase iron nitrides epsilon -Fe3N1+x with x=0.10, 0.22, 0.30, 0.33, 0.39 and a carbonitride epsilon -Fe-3(N0.80C0.20)(1.38) were investig ated by neutron diffraction, In these phases the non-metals occupy octahedr al interstices in an hcp arrangement of Fe. Type and degree of occupational order of N and N+C, respectively were determined as a function of composit ion and temperature. The ordering of N is closely related to that of the ep silon -Fe3N 'ideal' structure (space group P6(3)22). Neutron diffraction da ta on epsilon -Fe3N1.22 revealed lowered symmetry (P312). An earlier propos ed epsilon -Fe2N type ordering P (3) over bar 1m was not observed for the i ron nitride samples but it was found for epsilon -Fe-3(N0.80C0.20)(1.38). M agnetisation data show that the nitride and carbonitride phases are soft fe rromagnetic materials and confirmed magnetic structure data as derived from neutron diffraction. (C) 2001 Elsevier Science B.V. All rights reserved.