Microscopic spin-Hamiltonian parameters and crystal field energy levels for the low C 3 symmetry Ni 2+ centre in LiNbO 3 crystals

Abstract

The microscopic spin-Hamiltonian (MSH) parameters and the crystal field (CF) energy levels for Ni 2+ ions in LiNbO 3 crystals have been investigated using the crystal field analysis/microscopic spin-Hamiltonian package recently developed. The investigations considered for the first time the spin–spin (SS) and spin-other-orbit (SOO) interactions. The low-symmetry effects (LSE) arising from the additional terms (Im( B 43)≠0) induced at the C 3 symmetry sites by the distortion angle ϕ, which have been omitted in earlier works, have also been dealt with. This study shows that for LiNbO 3 : Ni 2+ the contributions arising from SS and SOO interactions to the zero-field splitting parameter D are appreciable, whereas those to g || and g ⊥ are quite small. Since the distortion angle ϕ (≅0.68°) for LiNbO 3 : Ni 2+ is rather small, the contributions to the spin-Hamiltonian (SH) parameters arising from LSE are also small. Feasibility of application of the superposition model is also discussed. A good overall agreement between the theoretical and experimental results for the SH parameters and the CF energy levels has been obtained.