Studies of the spin-Hamiltonian parameters and defect structures for the tetragonal and cubic Yb3+ centers in AgCl crystal.

The spin-Hamiltonian parameters, g factors and hyperfine structure constants, for the tetragonal and cubic Yb(3+) centers in AgCl crystal are calculated from the complete diagonalization (of energy matrix) method. The calculations are based on the defect models that the tetragonal Yb(3+) center is formed by the substitutional Yb(3+) associated with two nearest Ag(+) vacancy (V(Ag)) along <001> and <001¯> axes (i.e., C(4) axis) owing to charge compensation and in cubic Yb(3+) center the two compensators V(Ag) are remote. From the calculations, the spin-Hamiltonian parameters of both Yb(3+) centers in AgCl are explained reasonably, the signs of hyperfine structure constants A(i)((171)Yb(3+)) and A(i)((173)Yb(3+)) are suggested, the above defect models of both Yb(3+) centers are confirmed and their defect structures are determined.

Spin-Hamiltonian parameters and angular distortion for the trigonal Nd(3+) center in congruent LiNbO(3).

The 52x52 energy matrix related to the ground multiplet (4)I(9/2) and the first to third excited multiplets (4)I(11/2), (4)I(13/2) and (4)I(15/2) for 4f(3) ions in trigonal crystal field under an external magnetic field is established. By diagonalizing the energy matrix, the spin-Hamiltonian parameters (g factor g(parallel), g(perpendicular) and hyperfine structure constants (143)A(parallel), (143)A( perpendicular), (145)A(parallel), (145)A( perpendicular)) of the trigonal Nd(3+) center in congruent LiNbO(3) crystal are calculated. The calculated results are in reasonable agreement with the experimental values. From the calculations, the negative signs of hyperfine structure constants are suggested and the angular distortion of the trigonal Nd(3+) center in LiNbO(3), which is unable to be determined by EXAFS measurement, is obtained. The results are discussed.

Spin-Hamiltonian parameters and local structures for Co4+ and Ir4+ impurity centers in the tetragonal phase of SrTiO3.

The calculated results in the recent paper about the spin-Hamiltonian (SH) parameters (g factors g (//), g perpendicular and hyperfine structure constants A(//), A perpendicular) and the local structures of Co4+ and Ir4+ impurity centers in the tetragonal phase of SrTiO3 are doubtful because there are several mistakes in the calculations. So, we restudy the SH parameters and local structures by using the correct methods and parameters. From the studies, for Co4+ and Ir4+ in SrTiO3, the SH parameters are explained rationally, the signs of hyperfine structure constants A(//), A perpendicular are obtained and the suitable and more detailed local structures are given. The results are discussed.

Zero-field splittings and local tilting angles tauMn2+ for Mn2+ in ZnGeP2 and CdGeP2 crystals.

The electron paramagnetic resonance (EPR) zero-field splittings (ZFSs) D of Mn2+ in ZnGeP2 and CdGeP2 crystals are calculated from both the microscopic spin-orbit coupling mechanism and the empirical superposition model. From the calculations, the ZFS D of ZnGeP2:Mn2+ is reasonably explained by using the local tilting angle tauMn2+ (rather than the corresponding angle tauZn2+ in the host crystal) and the local tilting angle tauMn2+ (which has not been reported) in CdGeP2:Mn2+ is estimated. The intrinsic ZFS parameter b2(R0) approximately -0.052(6)cm(-1) (with R0 approximately 2.43 angstroms) is suggested for Mn2+-P(3-) combination by using the local tilting angles tauMn2+. The value is quite unlike that (approximately 0.4(2)cm(-1)) obtained in the previous paper by combining the crystallographic data of host crystals with the ZFSs for Mn2+ ions in crystals. The reasonableness of these results is discussed.