Structures,magnetic, and thermal properties of Ln3MoO7 (Ln = La, Pr, Nd, Sm, and Eu)

Ternary lanthanide-molybdenum oxides Ln(3)MoO(7) (Ln = La, Pr, Nd, Sm, Eu) have been prepared. Their structures were determined by X-ray diffraction measurements. They crystallize in a superstructure of cubic fluorite and the space group is P2(1)2(1)2(1). The Mo ion is octahedrally coordinated by six oxygens and the slightly distorted octahedra share corners forming a zig-zag chain parallel to the b-axis. These compounds have been characterized by magnetic susceptibility and specific heat measurements. The La3MoO7 shows complex magnetic behavior at 150 and 380 K. Below these temperatures, there is a large difference in the temperature-dependence of the magnetic susceptibility measured under zero-field-cooled condition and under field-cooled condition. The Nd3MoO7 show a clear antiferromagnetic transition at 2.5K. From the susceptibility measurements, both Pr3MoO7 and Sm3MoO7 show the existence of magnetic anomaly at 8.0 and 2.5 K, respectively. The results of the specific heat measurements also show anomalies at the corresponding magnetic transition temperatures. The differential scanning calorimetry measurements indicate that two phase-transitions occur for any Ln(3)MoO(7) compound in the temperature range between 370 and 7 10 K. (c) 2004 Elsevier Inc. All rights reserved.