EPR study of Fe3+ in α-quartz: A reexamination of the so-called I center

Abstract
10 GHz electron paramagnetic resonance studies of Fe3+ in synthetic brown α‐quartz single crystals have been carried out at 295 and at 40 K. The spin‐Hamiltonian parameters were determined including high‐spin Zeeman terms of form BS3 and allowing (g,D) matrix noncoaxiality as well as nonuniaxial anisotropy of the g matrix. Evaluation of the results, in part using the pseudosymmetry technique of Michoulier and Gaite, suggests that the so‐called interstitial model (I center) is incorrect, and that the Fe3+ ions in fact occur substitutionally at Si4+ sites. The new label [FeO4] is proposed for the center.

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