Microscopic spin-Hamiltonian parameters and crystal field energy levels for the low C₃ symmetry Ni²⁺ centre in LiNbO₃ crystals

The microscopic spin-Hamiltonian (MSH) parameters and the crystal field (CF) energy levels for Ni²⁺ ions in LiNbO₃crystals 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(B₄₃)≠0) induced at the C₃symmetry sites by the distortion angle ϕ, which have been omitted in earlier works, have also been dealt with. This study shows that for LiNbO₃: Ni²⁺ 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 LiNbO₃: Ni²⁺ 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. Copyright © 2003 Elsevier B.V. All rights reserved.