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

An electron paramagnetic resonance (EPR) study of a synthetic single crystal of LiScGeO4 doped with Cr ions carried out earlier at the X- and Q-bands at 300 K has indicated additional weak lines. A detailed analysis of these EPR lines, which were tentatively attributed to the Fe3+ ions at two different mirror symmetry sites, is presented in this paper. The angular dependences in the three crystallographic planes were resolved by fitting the two distinct spectra denoted Fe3+(I) and Fe3+(II) with a spin Hamiltonian (S = 5/2) of monoclinic symmetry. The rank-4 crystal field tensors at tetrahedral and octahedral sites were calculated with the point-charge model to determine the principal axis orientations of their cubic, tetragonal and trigonal components. A comparative analysis of the zero-field splitting tensors and the crystal field ones indicates that Fe3+(I) ions substitute for Sc3+ at octahedral sites and Fe3+(II) ions substitute for Ge4+ at tetrahedral sites with no significant distortion of the coordination polyhedra in the structure of LiScGeO4.