Paramagnetic susceptibility simulations from crystal field effects on rare earth antimonates R3Sb5O12

The magnetic susceptibilities of polycrystalline rare earth antimonates R₃Sb₅O₁₂ (R=rare earth), with cubic structure, space group I43m (No. 217), where the point site symmetry of R is S₄, have been measured from 4.2 to 800 K. Using the wave functions and energy levels derived from standard free ion and crystal field parameters deduced from the analysis of the optical spectra of pure and/or doped Pr, Nd, Eu and Er compounds, the calculation of the temperature dependent paramagnetic susceptibility has been carried out according to the Van Vleck formalism. The same calculation through crystal field parameters resulting from the ab initio simple overlap model over the entire R₃Sb₅O₁₂ series has been performed. Curves of both kinds were very similar for each configuration, with the exception of those for the Pr compound. Very good agreements with experimental data are found, especially below around 400 K, even when the approximate D_2d (near S₄) potential is considered. The standard crystal field treatment of 4f^N configurations is shown to explain the magnetic properties of these compounds with no need to consider any sort of magnetic interaction between the magnetic ions.