EPR of Fe³⁺ in Low Quartz Isomorphs A(III)B(V)O₄

Abstract

Electron spin resonance spectra of Fe 3+ in hydrothermally grown single crystals of A1P04 , GaP04, A1AS04 and GaAs04 were measured at X-band and analyzed using a Spin-Hamiltonian for rhombic symmetry. The zero field splitting was found to be between about one and two times the microwave frequency, increasing regularly from A1P04 to GaAs04. This increase is largely due to an increase in the axial parameter D whereas the second order rhombic parameter E is practically constant. The fourth order parameter a increases exponentially with the lattice parameter ratio c0/a0 . The variation of D indicates a site distortion for GaP04 about twice as large as in A1P04 . For the arsenates, influences of increased covalency are apparent in addition to site distortions of comparable size. Halfwidths in the range of 18 Gauss for the phosphates and 38 Gauss for the arsenates indicate hyperfine interactions with 31 P and 75 As, and estimates of 0.5 and 1% spin density resp. at these nuclei are obtained, again showing increased covalency for the arsenate compounds.

The structures of three centers of trivalent iron in ?-quartz

“…of accumulation of electron density from the ligands). This axis of compression along e is a common feature also for Fe 3+ in the AB04 isomorphs of quartz (A=A1, Ga; B-P; As) (Krauss and Lehmann 1975) whereas the monoclinic site symmetries only require the twofold axis to coincide with one of the principal axes. As shown by SPM analyses (Behner et al 1986) neither the substitutional nor the interstitial site on the twofold axis lead to such a ZFS pattern.…”

Physicochemical characteristics of iron-bearing lazulite from granitic pegmatites of the Patom Highlands, Irkutsk Region

“…Линии группы А обладают различной, в том числе очень высокой, интенсивностью и значительной анизотропией g-фактора. Их сложная угловая зависимость характерна для иона 3d 5 в 6 S-состоянии и подобна описанной для иона Fe 3+ , находящегося в позиции алюминия в фосфатах типа AlPO 4 (Krauß, Lehmann, 1975). На основании результатов химического анализа изученного нами образца можно предположить, что ион Fe 3+ является практически единственным кандидатом на такое замещение.…”