Analysis on the local structures for 3d ^{11 impurities (Ti 3+3+ and V 4+4+ ) in KTiPO ₄4}

摘要

> Making use of the perturbation formulae for 3d 1 ions (Ti 3+ and V 4+ ) under orthorhombically compressed octahedra, the spin Hamiltonian parameters (g factors: g _x , g _y , g _z and hyperfine structure constants: A _x , A _y , A _z ) and local structures of the 3d 1 impurity centres C ₁ , C ₂ , and C ₃ in KTiOPO ₄ crystals are theoretically analyzed in a consistent way. The remarkable local distortions (i.e., the relative axial compression ratios 11.2%, 7.0%, and 5.5% along Z axis and the relative planar bond length variation ratios 15.9%, 7.0%, and 6.0%) are obtained for the [Ti2O ₆ ] 9? cluster on Ti2 site and [VO ₆ ] 8? clusters on Ti1 and Ti2 sites, respectively, in view of the Jahn–Teller effect. The above local orthorhombic distortion parameters in the impurity centres are found to be more significant than the host Ti1 and Ti2 sites in pure KTiOPO ₄ . The sequences (C ₁ ??C ₂ ??C ₃ ) of the local orthorhombic distortion parameters ρ and τ are in accordance with those of the axial and perpendicular anisotropies Δg and δg of g factors, respectively.