Studies of the Angular Distortion around Ti3+ on the Trigonal (2a) Al3+ Site of LaMgAl11O19

The angular distortion around the impurity Ti³⁺ on the trigonal (2a) Al³⁺ site of LaMgAl₁₁O₁₉ is theoretically studied from the perturbation formulas of the anisotropic g factors, g_|| and g_⊥, for a 3d¹ ion in trigonally distorted octahedra. Based on the studies, the metal-ligand bonding angle is found to increase from θ_H in the host (2a) Al³⁺ site to θ in the impurity center by about 2^◦, due to the local tightness around the larger Ti³⁺ replacing the smaller Al³⁺. The theoretical results based on the above angular distortion are in reasonable agreement with the observed values.