Spin-Hamiltonian parameters and local rotational order parameters for Gd3+ ion in the tetragonal phase of SrTiO3 crystal

Using a diagonalization method, the spin-Hamiltonian parameters (g factors g||, g⊥ and zero-field splittings b20, b40, b24, b60, b64) for Gd3+ ion at the 12-fold coordinated Sr2+ site in the tetragonal phase of SrTiO3 at T≈4.2 and 77 K are calculated in a unified way. The calculated results are in reasonable agreement with the experimental values. The local rotational order parameters ϕl of Gd3+ center at the two temperatures are also obtained from the calculations. It is found that the local rotational order parameters ϕl of Gd3+ impurity center at both temperatures are different from the corresponding parameters ϕh in the host SrTiO3 crystal and the changes of spin-Hamiltonian parameters with temperature are caused by the change of local rotational order parameterϕl with temperature. The results are discussed.