A research on the g factors and defect model for the tetragonal Sm3+ center in KMgF3 crystal

Abstract The g factors g  and g ⊥ for the tetragonal (SmF 12 ) 9− cluster due to Sm 3+ occupying the 12-fold coordinated K + site in KMgF 3 perovskite are calculated from a diagonalization (of energy matrix) method. In the energy matrix, the crystal field parameters B k q used are calculated from the superposition model with the intrinsic parameters A ¯ k ( R 0 ) close to those of (GdF 12 ) 9− clusters for Gd 3+ in similar cubic perovskite c-RbZnF 3 . In the calculations, the applied defect model of tetragonal Sm 3+ center in KMgF 3 is that in which Sm 3+ occupies the 12-fold coordinated K + site associated with one (model A) or two (model B, where two K + vacancies are at both sides of Sm 3+ ) nearest K + vacancies along the C 4 axis for partial or complete charge compensation. The calculation results reveal that when the calculated g  and g ⊥ are in reasonable agreement with the experimental values, the tetragonal distortions of Sm 3+ centers are, whether in model A or model B, very small because of the slight anisotropy of the observed g factors. So, we suggest that the defect model of Sm 3+ center is that in which Sm 3+ occupies the 12-fold coordinated K + site associated with one or two next-nearest rather than nearest K + vacancies along the C 4 axis to result in small tetragonal distortions and hence in the small anisotropy of g factors. The reasonableness of our suggested defect model is discussed.