Magnetic properties of diluted magnetic „ Gd , Lu ...

The magnetic susceptibility of the diluted magnetic Lu22xGdxO3 ~x50.06, 0.10, 0.22, 0.40, 1.00, 1.40, 1.80! was measured in the temperature range 1.7–295 K. The inverse susceptibility changes slope to a smaller value below 2.2 K for the samples with x<0.40. In the cubic Lu0.20Gd1.80O3 the slope increases below 2.8 K. These changes are attributed to the large difference in susceptibility for two cationic sites at low temperatures and to the crystallographic distribution of Gd ions. The monoclinic Lu0.20Gd1.80O3, which was obtained from the stoichiometrically similar cubic phase at 1620 K, has an antiferromagnetic phase transition at 3.4 K. The magnetic-ion distribution for low-concentration samples ~x50.06, 0.10! was studied using an isolated-cluster method in the nearest-neighbor approximation. In these samples a tendency for magnetic-ion cluster formation was found. A random cluster distribution was found to be consistent with the susceptibility data for the sample with x50.06. For the x50.10 sample the susceptibility calculated with a modified cluster distribution gives the best agreement with the experimental results. @S0163-1829~98!00230-6#