Spin-Hamiltonian parameters, defect model and defect structure for the tetragonal Mo5+ center in x-ray-irradiated α-ZnMoO4 crystals

The spin-Hamiltonian (SH) parameters (g factors g∥ , g⊥ and hyperfine structure constants A∥, A⊥) for the Co2+ ion in the tetragonal Zn2+ site of a Ba2ZnF6 crystal are calculated from the secondorder perturbation formulas based on the cluster approach for the SH parameters of 3d7 ions in tetragonal symmetry with the effective spin S = 1/2. In the calculations, a reduction factor due to the dynamical Jahn-Teller effect is used. The calculated results are in reasonable agreement with the experimental values, suggesting that the dynamical Jahn-Teller effect should be considered here. The defect structure of the Co2+ center in Ba2ZnF6:Co2+ is also obtained from the calculations. The results are discussed.

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Theoretical Investigations of the Defect Structure for Ni3+ in ZnO

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.318.41 ◽

2011 ◽

Vol 318 ◽

pp. 41-45

Author(s):

Zhi Hong Zhang ◽

Shao Yi Wu ◽

Shan Xiang Zhang

Keyword(s):

Defect Structure ◽

Impurity Center ◽

Spin Hamiltonian ◽

Theoretical Investigations ◽

Ligand Orbital ◽

High Valence State ◽

Zno Crystal ◽

Hamiltonian Parameters ◽

Good Agreement ◽

The Ideal

The defect structure for Ni3+ in ZnO crystal is theoretically investigated using the perturbation formulas of the spin Hamiltonian parameters for a 3d7 ion in trigonally distorted tetrahedra. In view of the significant covalency of the system due to the high valence state of Ni3+, the ligand orbital and spin-orbit coupling contributions are taken into account in a uniform way based on the cluster approach. The impurity Ni3+ is found not to occupy the ideal Zn2+ site in ZnO but to undergo the small axial displacement of about 0.044 Ǻ away from the oxygen triangle along the C3 axis. The theoretical spin Hamiltonian parameters based on the above impurity displacement show good agreement with the experimental data. The defect structure of this impurity center is compared with that for the similar Fe3+ in ZnO.

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Investigations of the defect structure for Cu2+ in LaSrGa0.995Cu0.005O4 Ceramics

International Journal of Modern Physics B ◽

10.1142/s0217979215420151 ◽

2015 ◽

Vol 29 (25n26) ◽

pp. 1542015 ◽

Cited By ~ 1

Author(s):

C. C. Ding ◽

S. Y. Wu ◽

Y. K. Cheng ◽

L. J. Zhang

Keyword(s):

Hyperfine Structure ◽

Defect Structure ◽

Teller Effect ◽

Spin Hamiltonian ◽

Elongation Ratio ◽

Jahn Teller ◽

Jahn Teller Effect ◽

Structure Constants ◽

Hamiltonian Parameters ◽

The Relationship

The defect structure and spin Hamiltonian parameters ([Formula: see text] factors [Formula: see text], [Formula: see text] and the hyperfine structure constants [Formula: see text] and [Formula: see text]) for the tetragonal [Formula: see text] in [Formula: see text] ceramics are theoretically studied from the perturbation formulas of these parameters for a [Formula: see text] ion in a tetragonally elongated octahedron. The impurity [Formula: see text] center exhibits the larger relative tetragonal elongation ratio [Formula: see text] than that [Formula: see text] of the host [Formula: see text] site due to the Jahn–Teller effect. The relationship between the [Formula: see text] anisotropy [Formula: see text] [Formula: see text] and the local tetragonal distortion is analyzed. The present studies would be helpful to the understandings of delocalization of the [Formula: see text] [Formula: see text] orbitals under tetragonal elongation distortion and its role in superconductivity of oxygen cuprates.

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Theoretical Investigations for the Defect Structure and the Spin Hamiltonian Parameters of Divalent Cobalt in LiMgPO4

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1032.108 ◽

2021 ◽

Vol 1032 ◽

pp. 108-113

Author(s):

Xu Sheng Liu ◽

Shao Yi Wu ◽

Yi Mei Fan ◽

Xing Yuan Yu

Keyword(s):

Defect Structure ◽

Spin Hamiltonian ◽

Size Mismatch ◽

Local Structures ◽

Distorted Octahedral ◽

Theoretical Investigations ◽

Divalent Cobalt ◽

Structure Constants ◽

Relative Compression ◽

Hamiltonian Parameters

The spin Hamiltonian parameters (SHPs, g factors and hyperfine structure constants) defect structure for LiMgPO4 doped with 0.1% Co2+ at 4.2 K are theoretically investigated from the perturbation formulas of the SHPs for a rhombically distorted octahedral 3d7 cluster. The impurity Co2+ on host Mg2+ site is found to suffer the larger axial relative compression ratio ρ (≈ 0.76%) and the planar angular variation Δφ (≈ 6.64°) related to the host oxygen octahedron due to size mismatch. The calculated SHPs based on the above defect structure show good agreement with the measured results. Present study can be helpful to the preparation and characterization for the local structures for transition-metal impurities in lithium-magnesium phosphate, which may is helpful to search for the phosphor materials with better dosimetric characteristics.

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