Synthesis and magnetic properties of rare earth iron chromium phases and their nitrides

Synthesis, structural, and magnetic properties of R(3)(Fe,Cr)(29) intermetallic compounds (R=Ce,Nd) and their nitrides are reported. The Ce-3(Fe,Cr)(29) sample was single phase while the R=Nd ingot contained significant contamination by secondary phases. X-ray analysis reveals the monoclinic Nd-3(Fe,Ti)(29)-type structure with space group A2/m. The unit cell dimensions for the parent R=Ce compound are a=10.513(2) Angstrom, b=8.478(1) Angstrom, c=9.657(1) Angstrom, beta=96.75(1)degrees, and V=854.70 Angstrom(3). In the case of Ce a relative unit cell expansion of 6.5% is observed upon nitrogenation. The Curie temperature is 326 K for Ce and 432 K for Nd and becomes 612 and 633 K for Ce-nitride and Nd-nitride, respectively. The room temperature magnetization at 5 T is 58.2 A m(2)/kg for Ce and 104.1 A m(2)/kg for Nd and increases after nitrogenation to 109.8 and 127.2 A m(2)/kg for Ce and Nd, respectively. The average hyperfine field of the R=Ce compound at 85 K is 19.2 T. X-ray diffraction measurements on a magnetically aligned powder of Ce-3(Fe,Cr)(29) indicate that the magnetocrystalline anisotropy of the iron sublattice is most likely an in-plane type. Mossbauer spectrum analysis provided evidence that the Cr enters the dumbbell sites. (C) 1996 American Institute of Physics.