Investigations of the local structures and spin Hamiltonian parameters for the trigonal Rh4+ and Ir4+ centers in rhombohedral BaTiO3.

The local structures and spin Hamiltonian parameters (g factors and the hyperfine structure constants) of the Rh(4+)(4d(5)) and Ir(4+)(5d(5)) centers in rhombohedral BaTiO(3) are theoretically investigated from the formulas of these parameters for a nd(5) (n=4 and 5) ion with low spin (S=1/2) in a trigonally distorted octahedron. From the calculations, the impurity ions are found not to occupy exactly the host Ti(4+) site in BaTiO(3) but to suffer a slight inward shift ( approximately 0.13A) towards the center of the oxygen octahedron along the C(3) axis, yielding much smaller trigonal distortion as compared with that of the host Ti(4+) site.

Investigations on the local angular distortions and the spin-Hamiltonian parameters for Ni+ in sulfides.

The local angular distortions and the spin-Hamiltonian parameters (the g factors and the hyperfine parameters) for Ni(+) in ABS(2) (A=Cu, Ag; B=Al, Ga) ternary sulfides are theoretically investigated from the perturbation formulas of these parameters for 3d(9) ions in a tetragonally distorted tetrahedron. In view of the strong covalency of such systems, the ligand orbital and spin-orbit coupling contributions are taken into account using the cluster approach. The local impurity-ligand bond angles in the Ni(+) centers are found to be about 1.

Studies of the spin Hamiltonian parameters and local structure for ZnO:Cu2+.

The spin Hamiltonian parameters (the g factors and the hyperfine structure constants) and local structure for ZnO:Cu2+ are theoretically studied from the perturbation formulas of these parameters for a 3d9 ion under trigonally distorted tetrahedra. The ligand orbital and spin-orbit coupling contributions are taken into account from the cluster approach due to the significant covalency of the [CuO4](6-) cluster. According to the investigations, the impurity Cu2+ is suggested not to locate on the ideal Zn2+ site in ZnO but to undergo a slight outward displacement (approximately 0.