Gadolinium-doped SrF2: Dipole strengths and concentration effects influenced by dipole-dipole interactions

Abstract

In the first part of this article we describe electric-field-effect measurements in EPR. These experiments yield the dipole strength of the permanent dipoles in Sr${\mathrm{F}}_{2}$: ${\mathrm{Gd}}^{3+}$ and we found ${\ensuremath{\mu}}_{\mathrm{I}}=(0.34\ifmmode\pm\else\textpm\fi{}0.02) {10}^{\ensuremath{-}28}$ cm and ${\ensuremath{\mu}}_{\mathrm{II}}=(0.80\ifmmode\pm\else\textpm\fi{}0.04) {10}^{\ensuremath{-}28}$ cm. Meanwhile, a new theoretical description of the dipolar complex made it possible to calculate the dipole strengths and the results are very close to the measured values. The second part of this article describes a new way to study the dipole-dipole interaction. Since the dipole-dipole interaction is influenced by the total dipole concentration, and the concentration ratio of the two types of dipoles is influenced by the dipole-dipole interaction, we performed ionic-thermocurrent and EPR experiments to establish the concentration ratio of the different types of dipoles as a function of the total dipole concentration. Drastic changes in the ratio could be explained by the increasing dipole-dipole interaction with increasing total concentration.