Crystal Field Contributions Research Articles

A new interpretation of the ground state splitting in Gd3+

The individual ligand contributions to the dominant (quadrupole) component of the Gd3+ ground state splitting for nine compounds with zircon structure are determined. The results of this analysis show that the theoretical problems previously encountered in explaining the ground state splitting were due to an incorrect assumption about the relative sign of the crystal field and spin-Hamiltonian quadrupole contributions. It is argued that three basic mechanisms make contributions of a similar magnitude to the observed splitting.

Interpretation of Crystal-Field Parameters in the Rare-Earth-Substituted Garnets

Crystal-field parameters of Yb3+, Eu3+, Tm3+, Sm3+, Dy3+, and Er3+ ions in various garnet lattices have been analyzed using a development of the superposition model proposed by Bradbury and Newman. This effects, in principle, the separation of the crystal-field contributions of the different coordinated O2− ions and determines power laws and the angular distortion near substituted ions. A realistic separation of the contributions to the n = 4 parameters is obtained even when no allowance is made for local distortion. However, owing to their greater angular sensitivity, the contributions to the n = 6 parameters can only be separated if local angular distortions of up to 9° are allowed for. Results derived for single-ligand parameters and power laws are in good accord with theoretical results obtained for other rare-earth systems.

Adsorption on transition metal sulphates and adsorbent crystal field effects

The adsorption of CFCl3 on the anhydrous transition metal sulphates, manganese through zinc, with the exception of ferrous sulphate, has been studied at 20.0, 6.0 and –10.0°C. The differential entropy of adsorption suggests that CFCl3 behaves as a two-dimensional van der Waals gas on all the adsorbents. The isosteric heat of adsorption at zero surface coverage was greatest with those adsorbents having the largest crystal field stabilization energy. Attempts to predict a crystal field contribution to the heat of adsorption, based on assumed surface structures, has provided qualitative agreement with experiment.

Electron-Spin-Resonance Spectrum ofMn2+inβ−Ga2O3

The electron-spin-resonance spectrum of ${\mathrm{Mn}}^{2+}$ has been investigated in monoclinic $\ensuremath{\beta}\ensuremath{-}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ at 24 kMc/sec. It was found that the spectrum consists of a set of lines corresponding to a single type of environment. This spectrum (including the fine and $\ensuremath{\Delta}m=0$ hyperfine structure) is satisfactorily described by the spin Hamiltonian for ${\mathrm{Mn}}^{2+}$ in a rhombic crystal field with the following derived constants: ${A}_{z}=\ensuremath{-}87.7\ifmmode\pm\else\textpm\fi{}0.2$ G; ${A}_{y}=\ensuremath{-}85.6\ifmmode\pm\else\textpm\fi{}0.2$ G; ${g}_{z}=2.002$; ${g}_{y}=2.007$; $D=545.0$ G; $E=124.3$ G. The $y$ crystal-field axis is along the monoclinic axis (b) and the $z$ crystal-field axis makes an angle of 18\ifmmode^\circ\else\textdegree\fi{} with the $c$ crystal axis ($a>c$). Forbidden $\ensuremath{\Delta}m=\ifmmode\pm\else\textpm\fi{}1,\ifmmode\pm\else\textpm\fi{}2$ hyperfine transitions were also observed. From the separations between the $\ensuremath{\Delta}m=\ifmmode\pm\else\textpm\fi{}1$ doublets, a value of ${Q}^{\ensuremath{'}}=+0.9\ifmmode\pm\else\textpm\fi{}0.2$ G was obtained. On the basis of the axial crystal fields inferred from the measured values of ${Q}^{\ensuremath{'}}$ in $\ensuremath{\beta}\ensuremath{-}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ and in other oxide materials, it appears that the calculated crystal-field contribution to the $D$ parameter of ${\mathrm{Mn}}^{2+}$ does not explain the experimental results.