Structural and magnetic studies of manganese-containing pyrochlore oxides

The preparation of a number of manganese-containing pyrochlores of the type Ln(2)(MnSb)O-7, Ln = Sm-Dy and Y, and Bi-2(MnM)O-7, M = Nb, Ta and Sb, at ambient pressure is described. The structures were refined from powder X-ra y and/or neutron diffraction data and the Rietveld method. All the oxides o f the type Ln(2)(MnSb)O-7, Ln = Sm-Dy or Y, have a regular pyrochlore struc ture with the cubic cell parameter being strongly dependent on the ionic ra dii of the Ln(3+) cation. Bi,(MnM)O-7, M = Nb, Ta or Sb, also adopt a regul ar pyrochlore structure and their magnetic properties indicate that Mn2+ is present in these oxides. (C) 2000 Published by Elsevier Science S.A. All r ights reserved.