Transferred hyperfine interactions forYb3+ions inCsCaF3andCs2NaYF6single crystals: Experimental andab initiostudy

Abstract

The results of an electron-nuclear double resonance study of the cubic paramagnetic ${\mathrm{Yb}}^{3+}$ center in ${\mathrm{Cs}}_{2}\mathrm{Na}\mathrm{Y}{\mathrm{F}}_{6}$ and $\mathrm{Cs}\mathrm{Ca}{\mathrm{F}}_{3}$ single crystals are presented. The values and signs of the transferred hyperfine interaction (THFI) parameters for several neighboring shells are determined. It is found that the relevant parameters for the two studied matrices differ, in spite of the fact that the nearest environment of the rare earth ion is nearly identical. A first-principles theoretical analysis is performed for the THFI parameters of the first coordination shell of ${\mathrm{F}}^{\ensuremath{-}}$ ions. Several mechanisms of metal ion-ligand coupling are considered and it is found that one of them, ligand polarization, explains the difference observed for the THFI parameters in ${\mathrm{Cs}}_{2}\mathrm{Na}\mathrm{Y}{\mathrm{F}}_{6}$ and $\mathrm{Cs}\mathrm{Ca}{\mathrm{F}}_{3}$.