The microscopic spin-Hamiltonian parameters and the crystal field energy levels for Ni2+ ions in LiNbO3 crystals were investigated by using the crystal field analysis/microscopic spin-Hamiltonian package recently developed. The investigations considered for the first time the spin–spin and spin-other-orbit interactions. The low-symmetry effects arising from the additional terms, Im(B43) ≠ 0, induced at the C3 symmetry sites by the distortion angle, which had been omitted in earlier work, were also dealt with. This study showed that, for LiNbO3:Ni2+, the contributions arising from spin–spin and spin-other-orbit interactions to the zero-field splitting parameter D were appreciable, whereas those to g|| and g were quite small. Since the distortion angle (about 0.68°) for LiNbO3:Ni2+ was rather small, the contributions to the spin-Hamiltonian parameters arising from low-symmetry effects were also small. Feasibility of application of the superposition model was also considered. A good overall agreement between the theoretical and experimental results for the spin-Hamiltonian parameters and the crystal field energy levels was obtained.

Microscopic Spin-Hamiltonian Parameters and Crystal Field Energy Levels for the Low C3 symmetry Ni2+ Centre in LiNbO3 Crystals. Z.Y.Yang, C.Rudowicz, Y.Y.Yeung: Physica B, 2004, 348[1-4], 151-9