NEUTRON-DIFFRACTION ANALYSIS OF ND3FE29-XTX (T=TI, CR, MN)

Rietveld analysis of neutron-diffraction data from Nd3Fe29-xTx (T=Ti, Cr, and Mn) has been used to determine the location of the substitutio nal atoms and the magnetic moments. Reanalysis of the T=Ti data confir ms that the space group A 2/m is a better choice than P2(1)/c, which h ad previously been used to describe the structure. The Ti atom locatio ns and concentrations remain unaffected in the two space groups, but f or the other substituents the refined concentrations are well behaved in A2/m, whereas in P2(1)/c the refinements were unstable due to the s ymmetry relations between certain substituted sites. The site occupanc ies are analyzed in terms of steric and environment effects. A possibl e explanation for the high Curie temperature of the Cr compound is pro posed. (C) 1996 American Institute of Physics.