Theoretical studies of the g factors and local structure for Pt3+ in α-Al 2 O 3

Abstract

The anisotropic g factors and local structure for the trigonal Pt3+ centre in alpha-Al2O3 are theoretically investigated from the perturbation formulas of the g factors for a 5d(7) ion in trigonal symmetry. The Pt3+ impurity is found to experience an outward displacement by about 0.18 angstrom away from the centre of the oxygen octahedron along the C-3-axis. The calculated g factors based on the above axial displacement show good agreement with the observed values. Importantly, the pending problem of +3 valence state of the doped Pt in alpha-Al2O3 is theoretically clarified, and the possibility of Pt+ (5d(9)) is thus excluded in this work.