Electron-Spin-Resonance Absorption Spectrum of Trivalent Gadolinium in Single-Crystal Calcite

Abstract

The electron-spin-resonance absorption spectrum of trivalent gadolinium located as a cation substitution has been observed in naturally occurring single-crystal calcite. At 77\ifmmode^\circ\else\textdegree\fi{}K the principal fine-structure spectral parameters are determined to be ${g}_{\ensuremath{\parallel}}={g}_{\ensuremath{\perp}}=1.9918$, ${{b}_{2}}^{0}=\ensuremath{-}610.01$ Oe, ${{b}_{4}}^{0}=2.73$ Oe, and ${{b}_{6}}^{0}=1.85$ Oe. The hyperfine-structure-splitting parameters for $^{155}\mathrm{Gd}$ and $^{157}\mathrm{Gd}$ measured at 4.2\ifmmode^\circ\else\textdegree\fi{}K are 4.348 Oe and 5.702 Oe, respectively. Fine-structure doublet splittings and their angular variations in specific crystallographic planes are used to determine the parameters of the off-diagonal crystalline electric field operators.