Magnetic and nuclear structure of the perovskite-like oxides (LaBi)(0.7)Ca0.3MnO3

Progressive substitution of La by Bi in the mixed oxides (LaBi)(0.7)Ca0.3Mn O3 leads to great changes in the magnetic and transport properties of these compounds. From neutron diffraction experiments performed at D1B and D2B a pparatus in the ILL, we have observed changes in the magnetic structure fro m ferromagnetic La0.65Bi0.05Ca0.3MnO3 to antiferro Bi0.7Ca0.3MnO3. The inte rmediate compounds show antiferromagnetism in a crystalline plane and ferro magnetism in the perpendicular direction. The distance Bi-O turns out to be shorter than the La-O due to the covalent character of the former. This ca n explain the increasing localization of the 3d electrons of Mn atoms and t he insulating character of Bi0.7Ca0.3MnO3. (C) 2000 Elsevier Science B.V. A ll rights reserved.