Electron paramagnetic resonance study ofFe3+inα-quartz: Hydrogen-compensated center

Electron paramagnetic resonance and proton electron-nuclear double-resonance studies of a hydrogen-compensated ${\mathrm{Fe}}^{3+}$ (S=(5/2) center in synthetic iron-doped α-quartz have been carried out at 20 and 15 K, respectively. The spin-Hamiltonian parameters were determined, allowing anisotropy of the g matrix as well as [g,D,A${(}^1$H)]-matrix noncoaxiality, and including high-spin terms of the form $S^4$. Evaluation of the results gives strong evidence that the center (called $S_2$ by some workers) consists of a ${\mathrm{Fe}}^{3+}$ ion occurring substitutionally at a ${\mathrm{Si}}^{4+}$ site, charge compensated by an interstitial hydrogen ion. The label [${\mathrm{FeO}}_4$/${\mathrm{H}}^{+}$ ${]}^0$ is proposed for the center.