Magnetic moment and hyperfine field on Fe sites in RFe6Sn6 compounds

Electronic structure and hyperfine fields are calculated for antiferromagne tic YFe6Sn6 using the linear muffin-tin orbital method. The results show th at Fe atoms have a strong ferromagnetic character with a full majority-spin band. The Fe moment is 2.2 mu(B) while the Fermi contact term contributes a hyperfine field of 20 T at the natural lattice parameters. The hyperfine field is close to the experimental value of 22 T measured at low temperatur e. The calculation shows that the core s electrons contribute 24 T to the h yperfine field, but the its electron contributes it T in the opposite direc tion. Calculations using different unit cell volumes reveal that only the c ore electron contributions to the hyperfine field are proportional to the F e magnetic moment with a conversion factor of 11.8 T/mu(B); the 4s contribu tion is not. The large local Fe moment and small hyperfine field are simila r to those found in Fe2P and FeO. (C) 1998 American Institute of Physics. [ S0021-8979(98)51611-8].