Local structure and magnetism of LaxEu1−xPO4 solid solutions

By combining high spinning speed (60 kHz) and low-field (4.7 T) $³¹\mathrm{P}$ solid-state NMR with magnetic susceptibility measurements, we experimentally characterized a series of solid solutions belonging to the $\mathrm{L}{\mathrm{a}}_x\mathrm{E}{\mathrm{u}}_{1\ensuremath{-}x}\mathrm{P}{\mathrm{O}}₄$ ($0\ensuremath{\le}x\ensuremath{\le}1$) series. Analyses of the magnetic susceptibility data were carried out using the free ion model and crystal field theory calculations allowing to extract the electronic structure. The paramagnetic shifts of the P sites having one $\mathrm{E}{\mathrm{u}}³⁺$ cation in their surrounding were predicted by combining the determined crystal field and energy level values with density functional theory (DFT) calculations. For the $\mathrm{L}{\mathrm{a}}_0.9\mathrm{E}{\mathrm{u}}_0.1\mathrm{P}{\mathrm{O}}₄$ sample, these theoretical shifts gave a very good overall trend allowing the unambiguous attribution of each P site. This study paves the way for the future analysis of both magnetic susceptibility and NMR data for a broad range of materials containing paramagnetic rare-earth cations.