材料期刊网

The local structures and the EPR g factors g(parallel to) and g(perpendicular to) are theoretically studied for the tetragonal Ti(3+)-V(O) centers in BaTiO(3) bulks and thin films using the perturbation formulas of the g factors for a 3d(1) ion in tetragonally elongated octahedra and compressed tetrahedra, respectively, based on the cluster approach. For the Ti(3+)-V(O) center in BaTiO(3) bulks, the impurity Ti(3+) suffers the displacement away from the oxygen vacancy V(O) by about 0.15 angstrom along the C(4) axis due to the electrostatic repulsion of the V(O). Nevertheless, the Ti(3+)-V(O) center in BaTiO(3) thin films may exhibit the tetragonally compressed tetrahedron, characterized by the bond angle 55.88 degrees larger than that (approximate to 54.74 degrees) of an ideal tetrahedron. The quite different g factors (especially g anisotropies Delta g = g(parallel to) - g(perpendicular to)) for the two kinds of samples are discussed, in view of the dissimilar bonding or coordination environments (i.e., incomplete bonding in the thin films may lead to the lower coordination number).