Nuclear Resonance Spectrum of Al27 in Chrysoberyl

Abstract

The nuclear magnetic resonance spectrum of Al²⁷ in a single crystal of chrysoberyl (BeAl₂O₄)₄ has been investigated at room temperature in a field of 7800 gauss. The spectra obtained as the crystal was rotated about the three crystal axes have been interpreted on the basis of eight Al²⁷ sites of two distinct types, the four sites of each type differing only in the orientation of the principal field gradients. Quadrupole coupling constants and electric field asymmetry parameters at the two types of sites were determined to be $$\begin{array}{ccc}& \mathrm{\hspace{0.17em}\hspace{0.17em}}\mathrm{Type\; I\; site}& \mathrm{\hspace{0.17em}\hspace{0.17em}}\mathrm{Type\; II\; site}\\ C_z{\mathrm{=eQ\phi }}_{\mathrm{zz}}\mathrm{/h}& \text{2850±15\hspace{0.17em}}\mathrm{kc}/\sec & \text{2846±15\hspace{0.17em}}\mathrm{kc}/\sec \\ {\mathrm{\eta =(\phi }}_{\mathrm{xx}}{\mathrm{-\phi }}_{\mathrm{yy}}{\mathrm{)/\phi }}_{\mathrm{zz}}& \text{0.94±0.02}& \text{0.76±0.02}\end{array}$$ In addition, the orientation of the principal field gradients has been determined at each of the eight sites.