Environment of Fe3+ at the M2 and Si sites of forsterite obtained from EPR

Abstract

Electron paramagnetic resonance of a forsterite Mg2SiO4 crystal doped with 57Fe revealed two strong Fe3+ centers which can be unambiguously assigned to the M2 and Si sites. All the fourth order terms of the spin Hamiltonian were determined for the two centers. It is shown that the local environment of Fe3+ at M2 is distorted without any apparent pseudoaxial symmetry, while the environment of Fe3+ at the Si position exhibits a strong axial distortion along the crystallographic a direction. There is no immediate local charge compensation for the Mg2+ and Si4+ substitution by Fe3+ in the crystal.

Low-Symmetry Spin Hamiltonian and Crystal Field Tensors Analysis: Fe3+ in Natrolite

“…This result is consistent with the previous data (see, e.g., 15,17,21), suggesting the dominance of the cubic component in the ZFS tensor B 4 for Fe 3+ in octahedral and tetrahedral sites. Our method allows identification of the coordination complex of Fe 3+ impurity in structure even in the presence of distortion of the local environment.…”

“…The ZFS tensor B 4 for Fe 3+ at tetrahedral sites is mainly determined by its cubic component (15,17). The procedure (9) for extracting the maximum invariant component (MIC) of a given symmetry G s in the tensor B 4 was described in (6,11).…”

“…[1] is equivalent to the expanded form (8) of the ZFS Hamiltonians, whereas the operatorsT LM (11) belong to the category of the "normalized combinations of spherical tensor (NCST) operators" (8) introduced earlier in (13, 14); apart from the coefficient √ 2. Consequently the operatorsT LM are equivalent (to within the scaling factor for a given L) to the normalized Stevens (NS) operators of Gaite at al., e.g., (6,15); for details see (16) and the review (8). Explicit transformation formulas for the parameters B LM under coordinate rotations are given for L = 2, 4, 6 in (11,17).…”

Modeling EPR Powder Spectra Using Numerical Diagonalization of the Spin Hamiltonian

“…(i) Unresolved superhyperfine coupling with neighboring odd nuclear spins (e.g., 1 H, 27 Al, 31 P, 29 Si . .…”

Electron paramagnetic resonance study of Fe3+ ions at octahedral and tetrahedral mirror symmetry sites in the LiScGeO4 crystal

“…Fe 3+ ions in low concentrations ate usual traces in the natural and synthetic crystals with olivine type structure thus determining their spectroscopic properties. In forsterite Mg2SiO a, Fe 3+ ions were established as substituting at all the three structurally nonequivalent cationic sites [2,3]: the octahedral MI (4a) and M2 (4c) sites, and the tetrahedral (4c) sites. In chrysoberyl A12BeO 4, Fe 3+ ions were established as substituting for Al 3+ at the octahedral M2 site [4].…”