Mei-Ling Duan

Theoretical study of the dependence of EPR spectra on local structure for octahedral Cr(3+) centres in oxides and fluorides series

A theoretical method for investigating the inter-relation between the EPR parameters and local structure has been established on the basis of the complete energy matrices for 3d3 configuration ions in both the trigonal and tetragonal ligand fields. By means of this method, the local structure of the octahedral Cr3+ centres in double molybdates series and spinels series as well as the perovskite-type fluorides series has been studied systematically. Furthermore, the dependence of the EPR zero-field splitting parameter D on the local structure parameters in both trigonal and tetragonal ligand-fields has been revealed, simultaneously. The inter-relation between the EPR parameters D and Δg(g //  − g ⊥) is also elucidated.

Theoretical studies of EPR spectra and defect structure for Er3+ center in lithium niobate

The optical and EPR spectra of octahedral Er(3+) center in LiNbO(3) have been studied by diagonalizing 364 x 364 complete energy matrices. The new set of crystal-field parameters that can well account for the Stark levels and EPR parameters have been obtained for Er(3+) ions in LiNbO(3). Simultaneously, by simulating the most reliable six-order parameter B(60) obtained, we have presented the evidence that the Er(3+) ions do not occupy the actual Li(+) site, but have a displacement along the C(3)-axis away from the Li(+) center by about 0.0454 nm. The conclusion is well in accord with that drawn by earlier workers.

Structural, spectral characterization and electron paramagnetic resonance studies of Ni(2+) ions in various compounds: KZnF(3), CdCl(2), CdBr(2) and CsMgI(3)

The electron paramagnetic resonance (EPR) parameters (zero-field splitting D, and g-factors g ∥, g ⊥) for d 8 Ni2+ ions in tetragonal ligand fields KZnF3 : Ni2+ or in trigonal ligand fields CdCl2(CdBr2 and CsMgI3) : Ni2+ complexes have been systematically studied on the basis of the 45 × 45 complete energy matrices. The local structural distortion parameters of the crystals obtained are ΔR 1 = 0.0355 Å, ΔR 2 = 0.0296 Å for KZnF3 : Ni2+, ΔR = −0.1730 Å, Δθ = −1.5695○ for CdCl2 : Ni2+, Å, Δθ = −2.6236○ for CdBr2 : Ni2+ and ΔR = −0.0267 Å, Δθ = −1.8967○ for CsMgI3 : Ni2+. The calculated results show that the local structures exhibit elongation distortion for KZnF3 : Ni2+ and compression distortions for Ni2+ : CdCl2 (CdBr2 and CsMgI3) systems. Further, the relationships between ZFS parameter D and structural parameters (θ, R) are studied and the influence of the orbit reduction factor k on g-factors (Δg, g) are discussed.

Theoretical investigations of the local structure distortion and relationship between the EPR parameter and spin-orbit coupling coefficients for CsCdX3:Ni2+ (X = Cl, Br) systems

The EPR zero-field splitting parameters and structural distortion of Ni2+-doped CsCdX3 (X = Cl, Br) systems have been studied on the basic of 45f × 45 complete energy matrices for a configuration ion in trigonal ligand field, in which the contributions from the spin-orbit coupling coefficients of the central ions and ligands are taken into account simultaneously. It is shown that the local structure exhibits compression distortions for CsCdX3 (X = Cl, Br):Ni2+ systems, and the contribution from the s.o. coupling coefficient of ligands to the covalent effect should not be neglected. Simultaneously, the relationship between the EPR parameter D and the spin-orbit coupling coefficients (ζ, ) as well as the average parameter ζ1( ) and the divergent parameter ζ2( ) have been discussed.

Local defect structures and EPR studies on (FeO6)9− and (FeO4)5− clusters in YGG: Fe3+ system

The octahedral (FeO6)9− and tetrahedral (FeO4)5− clusters in yttrium gallium garnet (YGG): Fe3+ system are investigated based on the 252 × 252 complete energy matrices for d5 configuration ions in trigonal and tetragonal ligand fields, moreover, the EPR and optical spectra are made unified calculation. The results indicate that the defect structures around Fe3+ centres display expansion effects at different temperatures 4.2 and 295 K, and which are close to those in YIG garnet, respectively. Simultaneously, the defect structure parameters for Fe3+ centres in YGG are determined, and the relationship between the defect structure and the temperature has been discussed.