Nanopowders of La1-xMnO3+δ (with x = 0 to 0.3) were prepared at 825C by using a sol–gel method. As a result of chemical analyses and X-ray diffraction, 2 ranges of La/Mn ratios could be distinguished: for La/Mn < 0.9, phase separation into La0.9MnO3 and Mn3O4 occurred, while single phases with vacancies on both the La and Mn sites were obtained for La/Mn > 0.9. The La and Mn vacancy concentrations were deduced from combined Rietveld refinements of the X-ray and neutron diffraction data. The Curie temperature remained constant at a very high value of 295K for La/Mn < 0.9, but decreased at La/Mn ratios above 0.9. The decrease in Curie temperature was related to an increasing number of Mn vacancies; up to a limit which corresponded to a La0.93Mn0.93O3 compound with La/Mn = 1. In this compound, a cluster–glass behaviour was observed.

Influence of Cation Vacancies on Structural and Magnetic Properties of La1-xMnO3+δ Nanopowders. G.Dezanneau, O.Isnard, H.Roussel, A.Sin, M.Audier, H.Vincent: Crystal Engineering, 2002, 5[3-4], 347-54