Synthesis, structure determination and magnetic susceptibilities of the oxides Ln3Li5Sb2O12 (Ln ≠ Pr, Nd, Sm)

The oxides Ln₃Li₆Sb₂O₁₂ (Ln≠Pr, Nd, Sm) were prepared in air by heating a mixture of Ln₂O₃, LiNO₃and Sb₂O₃ in the temperature range 1023–1243 K. Lattice parameters as well as atomic coordinates in the space group 12,3 (Z≠8) are established from X-ray powder diffraction data by the Rietveld method. Magnetic susceptibilities from 4.2 to 300 K follow a Curie-Weiss law above 50 K (Ln≠Pr) or 70 K (Ln≠Nd). This is attributed to the splitting of the ground state associated with the Ln³⁺ ions by the influence of the crystal field. The magnetic moments, 3.54 and 3.61 μ_D for praseodymium and neodymium respectively, agree with those calculated by Hund's formula. The Sm³⁺ behaviour can be explained by taking into account that the splitting of the multiplets is not too large compared to kT. The magnetic moment observed at room temperature for this cation is 1.6 μ_B.