Electron-Nuclear Double Resonance ofMn2+inAl2O3

The electron paramagnetic resonance and electron-nuclear double resonance spectra of ${\mathrm{Mn}}^{2+}$ in ${\mathrm{Al}}_2$ ${\mathrm{O}}_3$ have been examined at 4.2°K. The spin-Hamiltonian parameters are ${\mathrm{g}}_{\mathrm{II}}$=2.0025±0.0006, $g_{\perp }=2.0010\mathrm{}\pm 0.002$, $D=+235.5\mathrm{}\pm 0.4$ G, $a-F=+24.7\mathrm{}\pm 0.6$ G, $A=-240.42\mathrm{}\pm 0.05$ Mc/sec, $B=-234.79\mathrm{}\pm 0.35$ Mc/sec, and $Q^{\prime }=+2.686\mathrm{}\pm 0.013$ Mc/sec. The quadrupole parameter $Q^{\prime }$ agrees with the value deduced from analysis of the "forbidden" ${\mathrm{Mn}}^{2+}$ spectrum and confirms the validity of that analysis. The axial crystal-field parameter increased significantly from the room-temperature value, and its absolute sign was shown to be positive.