Optical and Magnetic Properties of LiNbO₃:Ni²⁺

The optical and magnetic properties of the extensively interesting LiNbO₃: Ni²⁺ crystal, especially its zero-field splitting, have not been interpreted successfully so far. By the d⁸-C_3v^≠ complete energy matrix which includes all the t₂^meⁿS┌ terms and involves spin—orbit coupling and the trigonal crystal field, and also by the spin Hamiltonian theory, the present paper has given a uniform and complete strong—field calculation for the fine spectrum, the spin Hamiltonian parameters （D,g）, the ground state Zeeman splitting and the paramagnetic resonace conditions （H,hv） of LiNbO₃: Ni²⁺. With the spectrum parameters (in cm^-1 unit) B=790, C=3270, A=8300,ζ=530.5, v=-2400,v’=565.69, the calculated results are in very good agreement with the findings. Thus, the optical and paramagnetic properties of LiNbO₃: Ni²⁺ are well interpreted uniformly for the first time. Among the calculation results, D=-5.0734（-5.31） , g‖=2.2589（2.26±0.01）,g⊥=2.2613, hv=030017～0.30194(0.30021 cm^-1), the values in the parentheses are findings. It is shown that the g values, especially the EPR conditions and the D value, are extremelly sensitive to the contributions from excited terms, thus the utilization of complete energy matrix is necessary. The theoretical methods, including the g formulae, are suitable for arbitrary d⁸（or d²)-C_3v ions.