Paramagnetic susceptibility simulations from crystal field effects on Nd3+ in magnesium borate MgNd(BO2)5

Abstract

Abstract From the crystal field analysis of optical absorption spectra on monoclinic S.G. P21/c MgNd(BO2)5, where Nd3+ occupies a single crystallographic position with no symmetry elements, energy level schemes and an expression of the associated wavefunctions for the 4f3 configuration of Nd3+ have been derived, considering approximate C2v and Cs (C2) symmetries. Despite of the low symmetry of Nd3+, resulting rms deviations between calculated and experimental levels are very satisfactory. The composition of the crystal field wavefunctions from both sets of phenomenological free-ion and crystal field parameters has been checked through a calculation of the thermal evolution of the paramagnetic susceptibility χ, according to the Van Vleck formula. The same simulation was performed with crystal field parameters (CFPs) resulting from the ab initio simple overlap model (SOM), considering the Nd3+ real point symmetry, C1. Over the whole measured range, 1.7–375 K, and especially at low temperatures, a very good reproduction of the experimental χ vs. T is yielded by each of the experimental and SOM calculated collections of CFPs. The oversimplified SOM model seems thus to be useful providing reasonable estimations of crystal field strength parameters.