An X-ray diffraction and magnetic susceptibility study of TmxY2-xO3

The polycrystalline samples of TmxY2-xO3 (x = 0.1, 0.2, 0.4, 0.6, 1, 1.4, 1 .8) were obtained by ceramic technology. X-ray diffraction data were collec ted and the crystal structures were refined by the Rietveld method, A rando m distribution of Tm3+ ions over two cationic sites, 8b and 24d, in the spa ce group Ia (3) over bar was found. Magnetic susceptibility measurements of all samples were done using a SQUID susceptometer in a temperature range 4 K < T < 290 K, Above 90 K a Curie-Weiss law was observed, while below 90 K the inverse magnetic susceptibility deviates from linearity due to the cry stal-held influence. Deduced effective magnetic moments are close to the fr ee ion values. In the whole temperature range the susceptibility data were fitted in accordance with the axial symmetry approximation of the crystal f ield and corresponding values of the crystal-field energy levels were deduc ed. (C) 2000 Elsevier Science B.V. All rights reserved.