Theoretical studies of the g factors and local structure for the tetragonal Nd3+ center in SrTiO3

The anisotropic g factors g// and g⊥ and the local structure for the tetragonal Nd3+ center in SrTiO3 are theoretically studied using the perturbation formulas of the g factors for a 4f3 ion in tetragonal symmetry. This center is attributed to the impurity Nd3+ occupying the dodecahedral Sr2+ site in SrTiO3, associated with one nearest neighbour interstitial oxygen OI along [0 0 1] (or C4) axis. The impurity Nd3+ is found to suffer the large displacement (≈1.1 Å) towards the OI along the C4 axis due to their strong interaction. The calculated g factors based on the above impurity axial displacement show reasonable agreement with the experimental results.