Electron-Spin Resonances in Gamma-Ray-Irradiated Aluminum Oxide

Abstract

Single crystals of $\ensuremath{\alpha}$-aluminum oxide were subjected to gamma-ray irradiation at 77\ifmmode^\circ\else\textdegree\fi{}K. A single, asymmetric, paramagnetic-resonance absorption was produced with ${g}_{\mathrm{II}}=2.012\ifmmode\pm\else\textpm\fi{}0.002$ and ${g}_{\ensuremath{\perp}}=2.008\ifmmode\pm\else\textpm\fi{}0.002$, where \ensuremath{\parallel} and \ensuremath{\perp} are with respect to the $c$ axis. The line width is about 50 G at 300 and 77\ifmmode^\circ\else\textdegree\fi{}K. The absorption line has been analyzed as a superposition of three Gaussian lines with the isotropic $g$ values: ${g}_{1}=2.020\ifmmode\pm\else\textpm\fi{}0.003$, ${g}_{2}=2.006\ifmmode\pm\else\textpm\fi{}0.003$, ${g}_{3}=2.006\ifmmode\pm\else\textpm\fi{}0.003$. The component lines are tentatively attributed to two types of centers: a trapped hole localized on an anion adjacent to a cation site which is deficient in positive charge, and an electron trapped at an anion vacancy. The cation site may be vacant, or may contain a monovalent or divalent substitutional impurity.