Electron-Spin-Resonance Spectrum of Mn2+ in β−Ga2O3

Abstract

The electron-spin-resonance spectrum of ${\mathrm{Mn}}^{2+}$ has been investigated in monoclinic $\beta -{\mathrm{Ga}}_2{\mathrm{O}}_3$ 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 $\Delta m=0\mathrm{}$ hyperfine structure) is satisfactorily described by the spin Hamiltonian for ${\mathrm{Mn}}^{2+}$ in a rhombic crystal field with the following derived constants: $A_z=-87.7\mathrm{}\pm 0.2$ G; $A_y=-85.6\mathrm{}\pm 0.2$ G; $g_z=2.002\mathrm{}$; $g_y=2.007\mathrm{}$; $D=545.0\mathrm{}$ G; $E=124.3\mathrm{}$ G. The $y$ crystal-field axis is along the monoclinic axis (b) and the $z$ crystal-field axis makes an angle of 18° with the $c$ crystal axis ($a>c$). Forbidden $\Delta m=\pm 1,\pm 2$ hyperfine transitions were also observed. From the separations between the $\Delta m=\pm 1$ doublets, a value of $Q^{\prime }=+0.9\mathrm{}\pm 0.2$ G was obtained. On the basis of the axial crystal fields inferred from the measured values of $Q^{\prime }$ in $\beta -{\mathrm{Ga}}_2{\mathrm{O}}_3$ 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.