Local environment of optically active Nd3+ions in the ultratransparent BaMgF4ferroelectric crystal

Abstract

A comprehensive study of the site location of Nd${}^{3+}$ ions in the BaMgF${}_{4}$ ultratransparent ferroelectric crystal is presented. By combining different low-temperature optical spectroscopies and electron paramagnetic resonance, the crystal field energy levels of Nd${}^{3+}$ ions and the gyromagnetic factors are experimentally determined. These results are employed to perform the crystal field analysis of Nd${}^{3+}$ ions considering a Cs point symmetry. The crystal field calculation yields a small root-mean-square deviation of 18 cm${}^{\ensuremath{-}1}$ and reveals a large crystal field strength (621 cm${}^{\ensuremath{-}1}$), verifying the assignment of the Ba${}^{2+}$ cationic site as the location for Nd${}^{3+}$ ions in this fluoride host. The results suggest a slight displacement of Nd${}^{3+}$ from the barium regular site with a rearrangement of the fluorine ions around it. The work gives a deep insight into the properties of the Nd${}^{3+}$-doped BaMgF${}_{4}$ crystal, a ferroelectric widely ultra-transparent material with potential applications as optical device operating in the Vacuum Ultraviolet-Ultraviolet and midinfrared spectral regions.