Site occupancy of Sm in (Nd1-xSmx)(5)(Fe1-yTiy)(17)

The ferromagnetic compound Nd5Fe17 has a large average Fe moment (2.1 mu(B) ), a reasonably high Curie temperature (503 K), but basal plane spin orient ation. Partial replacement of Nd by Sm leads to a uniaxial spin arrangement with substantial anisotropy field. Natural Sm has a large neutron absorpti on cross section (5650 b) which is usually thought to prevent neutron diffr action measurements unless Sm is replaced by a separated isotope with low a bsorption. However, the unique geometry of the MURR neutron powder diffract ometer allows measurements on thin samples and data have been successfully collected on samples with up to about 50% Sm (Nd2.5Sm2.5Fe17). Samples prep ared without Ti contain the 2:17 phase as well as the 5:17 phase, while tho se prepared with Ti have a very high concentration of the 5:17 phase which forms more readily (with minor amounts of TiFe2). The locations of Sm atoms in these compounds have been determined. These results may provide importa nt information about the crystal fields at different sites in the 5:17 phas e and suggest improved routes for synthesis of this potentially useful comp ound. (C) 2000 American Institute of Physics. [S0021-8979(00)77108-8].