THEORETICAL STUDIES OF THE SPIN HAMILTONIAN PARAMETERS AND LOCAL STRUCTURE FOR THE TETRAGONAL Rh2+ CENTER IN RHOMBOHEDRAL BaTiO3

2009 ◽  
Vol 23 (17) ◽  
pp. 2115-2122 ◽  
Author(s):  
HUA-MING ZHANG ◽  
SHAO-YI WU ◽  
XUE-FENG WANG ◽  
YUE-XIA HU
Keyword(s):  
Local Structure ◽  
Relative Elongation ◽  
Experimental Results ◽  
Teller Effect ◽  
Theoretical Studies ◽  
Spin Hamiltonian ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Hamiltonian Parameters ◽  
Good Agreement

The spin Hamiltonian parameters and local structure for the tetragonal Rh 2+ center in rhombohedral BaTiO 3 are theoretically studied from the perturbation formulas of these parameters for a 4d 7 ion with low spin (S=1/2) in tetragonally elongated octahedra. This center is ascribed to substitutional Rh 2+ at the Ti 4+ site in BaTiO 3. The [ RhO 6]10- cluster suffers relative elongation (characterized by the elongation parameter ρ ≈ 0.9%) along the [100] axis due to the Jahn–Teller effect. The tetragonal elongation can entirely depress the slight trigonal distortion of the original Ti 4+ site in rhombohedral BaTiO 3. The calculated spin Hamiltonian parameters based on the above Jahn–Teller elongation show good agreement with the experimental results.

scholarly journals Investigations of the Spin Hamiltonian Parameters and the Local Structures of the Substitutional V4+ Centres in Rutile-Type MO2 (M = Sn, Ti, Ge)

2008 ◽  
Vol 63 (7-8) ◽  
pp. 523-528 ◽  
Author(s):  
Shao-Yi Wu ◽  
Li-Hua Wei ◽  
Zhi-Hong Zhang ◽  
Xue-Feng Wang ◽  
Ji-Zi Lin
Keyword(s):  
Experimental Data ◽  
Teller Effect ◽  
Oxygen Octahedra ◽  
Spin Hamiltonian ◽  
Local Structures ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Hamiltonian Parameters ◽  
Good Agreement

The spin Hamiltonian parameters and the local structures of the substitutional V4+ centres in rutiletype MO2 (M = Sn, Ti and Ge) are theoretically investigated from the perturbation formulas of these parameters for a 3d1 ion in a rhombically compressed octahedron. The oxygen octahedra around V4+ are found to transform from the original elongation on the host M4+ site to compression in the impurity centres due to the Jahn-Teller effect. The calculated spin Hamiltonian parameters based on the above local structures show good agreement with the experimental data.

Studies of the local structures and spin Hamiltonian parameters for the two Rh2+ centers in AgBr

2011 ◽  
Vol 89 (2) ◽  
pp. 177-183 ◽  
Author(s):  
Hua-Ming Zhang ◽  
Shao-Yi Wu ◽  
Pei Xu
Keyword(s):  
Experimental Data ◽  
Relative Elongation ◽  
Electrostatic Repulsion ◽  
Spin Hamiltonian ◽  
Local Structures ◽  
Charge Compensator ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Hamiltonian Parameters ◽  
Good Agreement

The local structures and the spin Hamiltonian parameters (the g-factors g|| and g⊥ and the superhyperfine parameters A||′ and A⊥′) are quantitatively studied for the two Rh2+ L and H centers (denoting the tetragonally elongated and compressed [RhBr6]4− clusters at low and high temperatures, respectively) in AgBr using the perturbation formulas of these parameters for a 4d7 ion in tetragonally elongated and compressed octahedra. From the studies, the elongated L center originates from the relative elongation of the parallel Rh2+–Br− bonds by about 0.081 Å along the C4 axis because of the Jahn–Teller effect. Nevertheless, the compressed center H is attributed to one next nearest neighbouring Ag+ vacancy VAg along the C4 axis as the charge compensator, which compels the intervening ligand Br− in the Rh2+ and the VAg to shift away from the latter by about 0.148 Å because of the electrostatic repulsion. All the calculated spin Hamiltonian parameters based on the above local structures are in good agreement with the experimental data for both centers.

Investigations on the Spin Hamiltonian Parameters and the Local Structures for Various Rh2+ Centers in NaCl

2010 ◽  
Vol 65 (6-7) ◽  
pp. 591-598 ◽  
Author(s):  
Hua-Ming Zhang ◽  
Shao-Yi Wu ◽  
Pei Xu ◽  
Li-Li Li
Keyword(s):  
Relative Elongation ◽  
Spin Hamiltonian ◽  
Local Structures ◽  
Tetragonal Center ◽  
Unpaired Spin ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Structure Constants ◽  
Hamiltonian Parameters ◽  
Spin Densities

The spin Hamiltonian parameters (the g factors, the hyperfine structure constants, and the superhyperfine parameters) and the local structures for various Rh2+ centers OI, OII, and RTAX in NaCl are theoretically investigated from the perturbation formulas of these parameters for a 4d7 ion in tetragonally and orthorhombically elongated octahedra. The related molecular orbital coefficients and the ligand unpaired spin densities are determined quantitatively from the cluster approach in a uniform way. The centers OI, OII (orthorhombic) or RTAX (tetragonal) are attributed to the substitutional Rh2+ on Na+ site, associated with two, one or none next nearest neighbour cation vacancies VNa along [100] (or [010]) axis, respectively. The ligand octahedra in the orthorhombic centers OI and OII are found to suffer the relative elongations ΔZ ≈0.071 and 0.068 °A along the [001] axis due to the Jahn-Teller effect, and the intervening ligand(s) in the VNa and the Rh2+ may undergo the inward displacements ΔX ≈ 0.001 and 0.011 A° towards Rh2+, respectively. As for the tetragonal center RTAX, the uncompensated [RhCl6]4− cluster is found to experience the relative elongation ΔZ ≈ 0.067 °A along the [001] axis of the Jahn-Teller nature. The calculated spin Hamiltonian parameters based on the above local structures show good agreement with the observed values for all the centers.

INVESTIGATIONS OF THE SPIN HAMILTONIAN PARAMETERS AND THE LOCAL STRUCTURE FOR THE RHOMBICCu2+CENTER IN RUTILE

2010 ◽  
Vol 24 (22) ◽  
pp. 2357-2364 ◽  
Author(s):  
HUA-MING ZHANG ◽  
SHAO-YI WU ◽  
PEI XU ◽  
LI-LI LI
Keyword(s):  
Local Structure ◽  
Impurity Center ◽  
Angular Distortion ◽  
Spin Hamiltonian ◽  
Rhombic Distortion ◽  
Calculation Results ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Structure Constants ◽  
Hamiltonian Parameters

The spin Hamiltonian parameters (the anisotropic g factors and the hyperfine structure constants) and the local structure for the rhombic Cu2+center in rutile ( TiO2) are theoretically investigated using the formulas of these parameters for a 3d9ion in rhombically elongated octahedra. From the studies, the planar impurity-ligand bond angle is found to be about 5.8° larger than that for the host Ti4+site due to the Jahn–Teller effect via bending the planar Cu2+– O2-bonds, which yields much smaller rhombic distortion in the impurity center. The theoretical spin Hamiltonian parameters based on the above local angular distortion show good agreement with the experimental data, and the improvement of the calculation results are also achieved as compared with those of the previous works.

A Study of Spin-Hamiltonian Parameters and Defect Structure for Co2+ Ion in the Tetragonal Zn2+ Site of Ba2ZnF6 Crystal

2010 ◽  
Vol 65 (10) ◽  
pp. 877-881
Author(s):  
Bang-Xing Lia ◽  
Wen-Chen Zheng ◽  
Wei-Qing Yang
Keyword(s):  
Defect Structure ◽  
Reduction Factor ◽  
Teller Effect ◽  
Tetragonal Symmetry ◽  
Spin Hamiltonian ◽  
Effective Spin ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Experimental Values ◽  
Hamiltonian Parameters

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.

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

2015 ◽  
Vol 29 (25n26) ◽  
pp. 1542015 ◽  
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.

Theoretical Investigations of the Spin Hamiltonian Parameters and Defect Structure for Pt3+ in MgO

2009 ◽  
Vol 293 ◽  
pp. 71-76
Author(s):  
Yue Xia Hu ◽  
Shao Yi Wu ◽  
Xue Feng Wang ◽  
Li Li Li
Keyword(s):  
Defect Structure ◽  
Relative Elongation ◽  
Impurity Center ◽  
Spin Hamiltonian ◽  
Theoretical Investigations ◽  
Ligand Orbital ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Structure Constants ◽  
Hamiltonian Parameters

The spin Hamiltonian parameters (anisotropic g-factors and the hyperfine structure constants) and defect structure for Pt3+ in MgO are theoretically investigated by using the perturbation formulas of these parameters for a 5d7 ion in a tetragonally elongated octahedron. This impurity center is attributed to substitutional Pt3+ on host Mg2+ sites, and the [PtO6]9 cluster suffers a relative elongation of 0.08Å along the C4 axis due to the Jahn-Teller effect. In the calculations, the contributions arising from the ligand orbital and spin-orbit coupling interactions and the Jahn-Teller elongation are taken into account using the cluster approach. The calculated spin Hamiltonian parameters based upon the above defect structure show good agreement with the observed values.

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