Electron Spin Resonance ofEr3+in CaF2

Abstract

Five different spectra of ${\mathrm{Er}}^{3+}$ in Ca${\mathrm{F}}_2$ were observed. One spectrum corresponds to a field of cubic symmetry with $g=6.785\mathrm{}\pm 0.002$; and one corresponds to a field of trigonal symmetry brought about by a substitution of ${\mathrm{O}}^{2-}$ ions for ${\mathrm{F}}^{-}$ ions, with $g_{\mathrm{II}}=2.206\mathrm{}\pm 0.007$, $g_{\perp }=8.843\mathrm{}\pm 0.01$. A third spectrum, also of trigonal symmetry with $g_{\mathrm{II}}=3.30\mathrm{}\pm 0.01$, $g_{\perp }=8.54\mathrm{}\pm 0.02$ is thought to be caused by a substitutional O${\mathrm{H}}^{-}$ ion. A spectrum of tetragonal symmetry with $g_{\mathrm{II}}=1.746\mathrm{}\pm 0.002$ and $g_{\perp }=9.16\mathrm{}\pm 0.01$ is believed to arise from sites of ${\mathrm{Er}}^{3+}$ ions with interstitial ${\mathrm{F}}^{-}$ ions in adjacent cubes. A fifth spectrum, for which the compensating ion is not identified, has tetragonal symmetry, with $g_{\mathrm{II}}=7.78\mathrm{}\pm 0.02$ and $g_{\perp }=6.254\mathrm{}\pm 0.005$. The data permit the evaluation of the nuclear magnetic moment of ${\mathrm{Er}}^{167}$ as ${\mu }_N=0.56\mathrm{}\pm 0.05$ nuclear magnetons.