EPR, ENDOR, and optical spectroscopy of the tetragonalYb3+center inKMgF3

Abstract

Electron paramagnetic resonance, electron-nuclear double resonance, and optical spectroscopy of the tetragonal ${\mathrm{Yb}}^{3+}$ center in ${\mathrm{KMgF}}_{3}$ are reported here. The results of these experiments allow us to conclude that a previously given structural model as well as the interpretation of the optical spectrum of this center are incorrect. A model is presented and experimentally and theoretically justified. In particular, the values of the hyperfine and transferred hyperfine interaction parameters were determined as well as an experiment-based energy-level scheme. Its parametrization is performed by including simultaneously the crystal field and the spin-orbit interaction within the ${}^{7}\mathrm{F}$ term. Furthermore, a theoretical analysis of the transferred hyperfine interaction (THFl) parameters is presented. It is further shown from optics and from microscopic calculations of the THFI parameters that ${g}_{\ensuremath{\parallel}}$ and ${g}_{\ensuremath{\perp}}$ have opposite signs and that the rule of correspondence between the cubic g factor and $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{g}=\frac{1}{3}{(g}_{x}{+g}_{y}{+g}_{z})$ does not depend on the relative magnitude of the cubic and low-symmetry crystal field acting on the rare-earth ion.