scholarly journals Defect Structures for Fe3+, Mn2+, and Ni3+ Impurities in Wuritzite GaN Crystals

2001 ◽  
Vol 56 (6-7) ◽  
pp. 473-477 ◽  
Author(s):  
Wen-Chen Zheng ◽  
Shao-Yi Wu ◽  
Jian Zi
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Strong Field ◽  
Zero Field ◽  
Spin Orbit ◽  
Defect Structures ◽  
Superposition Model ◽  
Paramagnetic Resonance ◽  
Impurity Ions ◽  
Epr Parameters ◽  
Electron Paramagnetic

Abstract Electron paramagnetic resonance (EPR) zero-field splittings D for Mn2+ and Fe3+ in wurtzite GaN crystals are studied from high-order perturbation formulas based on the spin-orbit mechanism in both weak- and strong-field schemes. From these studies it can be seen that the Mn2+ or Fe3+ impurity does not occupy the exact Ga3+ position, but is displaced by ΔR on the C3 axis. The displacements are confirmed from a study of the superposition model, based on which a normal value of b̅2 (Ro) ( ≈ -0 .34 (15) cm-1 ) for the Fe3+-N3- combination is suggested. The EPR parameters D, g|| and g ⟂ for Ni3+ in GaN crystals are also studied. It is found that Ni3+ is almost not displaced. The impurity displacements in GaN are discussed by considering the valences and radii of these impurity ions and the replaced Ga3+ ion. - Pacs: 61.16Hn; 76.30Fc; 71.70Ch

Investigations of the EPR Parameters and Local Structures for Two Tetragonal Cr3+ Centers in NH4Cl Crystal

2001 ◽  
Vol 56 (3-4) ◽  
pp. 326-328 ◽  
Author(s):  
Shao-Yi Wu ◽  
Wen-Chen Zheng
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Room Temperature ◽  
Zero Field ◽  
Spin Orbit ◽  
Zero Field Splitting ◽  
Paramagnetic Resonance ◽  
Resonance Parameters ◽  
Local Structures ◽  
Epr Parameters ◽  
Electron Paramagnetic

Abstract In this paper, the zero-field splittings D and g factors g||, g⟂ at room temperature for two tetragonal Cr3+ centers in NH4Cl:Cr3+ crystal have been investigated by a two-spin-orbit (S.O)-parameter model, in which both the contribution due to the S.O. coupling of central d3 ion and that of ligands are considered. From the investigations, the signs of zero-field splitting and the local structures of both centers are ob­ tained. The electron paramagnetic resonance parameters D, g|| and g⟂ of both centers are also explained.

INVESTIGATIONS OF ELECTRON-PARAMAGNETIC-RESONANCE PARAMETERS OF OCTAHEDRAL (CrO6)9- and (MnO6)8- CLUSTER IN MgTiO3:Cr3+, SrTiO3:Cr3+ AND SrTiO3:Mn4+ CRYSTALS

2011 ◽  
Vol 25 (21) ◽  
pp. 1779-1785
Author(s):  
MINJIE WANG ◽  
LIANXUAN ZHU ◽  
JIANLIANG DANG
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Crystal Field ◽  
Valence State ◽  
Spin Orbit ◽  
Contribution Rate ◽  
Paramagnetic Resonance ◽  
Epr Parameters ◽  
Experimental Values ◽  
Electron Paramagnetic ◽  
G Factors

The complete high-order perturbation formulas are established by both crystal-field (CF) and charge-transfer (CT) mechanisms. The EPR g factors of MgTiO 3: Cr 3+, SrTiO 3: Cr 3+ and SrTiO 3: Mn 4+ crystals are calculated from the formulas. The calculations of the EPR g factors are in agreement with the experimental values. The contribution rate of the CT mechanism (|ΔgT/ΔgF|) to EPR parameters, increases with the growth of the valence state for the 3dn ions in the crystals. For the higher valence state 3d3 ion Mn 4+ in crystals, the explanation of the EPR parameters reasonably involves both CF and CT mechanisms. The g values are also given from one-spin-orbit-parameter model and crystal-field (CF) mechanism for comparison.

On The EPR Parameters of Divalent Cobalt in ZnX (X = S, Se, Te) And CdTe

2004 ◽  
Vol 59 (12) ◽  
pp. 938-942 ◽  
Author(s):  
Shao-Yi Wu ◽  
Hui-Ning Dong
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Charge Transfer ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Paramagnetic Resonance ◽  
A Value ◽  
Epr Parameters ◽  
Divalent Cobalt ◽  
Structure Constants ◽  
Electron Paramagnetic

The electron paramagnetic resonance (EPR) parameters g and the hyperfine structure constants A of Co2+ in ZnX (X = S, Se, Te) and CdTe are studied, using the perturbation formulas of the EPR parameters for a 3d7 ion in tetrahedra based on two mechanism models. In these formulas, both the contributions from the conventional crystal-field (CF) mechanism and those from the charge-transfer (CT) mechanism are taken into account. According to the investigations, the sign of the g-shift ΔgCT from the CT mechanism is the same as ΔgCF from the CF mechanism, whereas the contributions to the A value from the CF and CT mechanisms have opposite signs. Particularly, the contributions to the EPR parameters from the CT mechanism increase rapidly with increase of the spin-orbit coupling coefficient of the ligand and the covalency effect of the systems, i. e. S2− < Se2− < Te2−.

Theoretical Studies of the EPR Parameters of Nd3+ in LiYF4

2004 ◽  
Vol 59 (4-5) ◽  
pp. 235-238 ◽  
Author(s):  
Shao-Yi Wu ◽  
Hui-Ning Dong
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Crystal Field ◽  
Structural Parameters ◽  
Tetragonal Symmetry ◽  
Theoretical Studies ◽  
Superposition Model ◽  
Paramagnetic Resonance ◽  
Epr Parameters ◽  
Crystal Field Parameters ◽  
Electron Paramagnetic

The perturbation formulas of the electron paramagnetic resonance (EPR) parameters g∥, g⊥, A∥ and A⊥ for a 4f3(Nd3+) ion in tetragonal symmetry are established in this work. In these formulas, the contributions to the EPR parameters arising from the second-order perturbation terms and the admixtures of different states are included. Then the above formulas are applied to a tetragonal Nd3+ center in LiYF4, where the related crystal-field parameters are calculated from the superposition model and the local structural parameters of the Y3+ site occupied by the impurity Nd3+. The EPR parameters and the optical spectra within the 4I9/2 and 4I11/2 states obtained in this work agree reasonably with the observed values.

Investigation of the EPR Parameters and Defect Structure of Ni2+ Ions in RbMgF3 Crystals

2007 ◽  
Vol 62 (3-4) ◽  
pp. 221-223
Author(s):  
Tai-Hong Chen ◽  
Wen-Lin Feng ◽  
Jin-Ping Zhang
Keyword(s):  
Defect Structure ◽  
Defect Structures ◽  
Superposition Model ◽  
Energy Matrix ◽  
Paramagnetic Resonance ◽  
Epr Parameters ◽  
Matrix Diagonalization ◽  
Complete Energy Matrix ◽  
Electron Paramagnetic ◽  
61.72 Bb

By means of the complete energy matrix diagonalization procedure of 3d2/3d8 ions in trigonal symmetry and using the superposition model, the electron paramagnetic resonance (EPR) parameters for Ni2+ ions in RbMgF3 crystals with C3v and D3d symmetry are studied. From the investigation, the defect structures of these paramagnetic impurity centers are obtained and the EPR parameters are explained reasonably. - PACS numbers: 76.30.Fc, 61.72.Bb, 71.70.Ch

scholarly journals Investigation Of The Epr Parameters Of An Orthorhombic Cu2+ Center In Cs2zncl4 Crystal

2005 ◽  
Vol 60 (5) ◽  
pp. 373-375 ◽  
Author(s):  
Hui-Ning Dong ◽  
Shao-Yi Wu ◽  
Xian-Rong Liu ◽  
Wei-Dong Chen
Keyword(s):  
Crystal Structure ◽  
Electron Paramagnetic Resonance ◽  
Hyperfine Structure ◽  
Hamiltonian Matrix ◽  
Superposition Model ◽  
Paramagnetic Resonance ◽  
Epr Parameters ◽  
Structure Constants ◽  
Crystal Field Parameters ◽  
Electron Paramagnetic

The electron paramagnetic resonance (EPR) anisotropic g-factors gx, gy and gz and hyperfine structure constants Ax, Ay and Az of Cu2+ in Cs2ZnCl4 crystal are theoretically investigated by the method of diagonalizing the full Hamiltonian matrix. The crystal-field parameters are obtained from the crystal structure by the superposition model. The results, agreeing reasonably with the observed values, are discussed.

Investigations of the Defect Structures and EPR Parameters for the Tetragonal and Cubic Ni2+ Centers in AgX (X=Cl, Br)

2008 ◽  
Vol 272 ◽  
pp. 117-122
Author(s):  
Zhi Hong Zhang ◽  
Shao Yi Wu ◽  
Li Hua Wei ◽  
Yue Xia Hu
Keyword(s):  
Experimental Data ◽  
Reasonable Agreement ◽  
Zero Field ◽  
Nearest Neighbour ◽  
Defect Structures ◽  
Cluster Approach ◽  
Zero Field Splitting ◽  
Paramagnetic Resonance ◽  
Epr Parameters ◽  
Electron Paramagnetic

The defect structures and the electron paramagnetic resonance (EPR) parameters zero-field splitting and the g factors for the tetragonal and cubic Ni2+ centers in AgX (X=Cl, Br) are theoretically studied from the perturbation formulas of these parameters for a 3d8 ion in tetragonal and cubic octahedra. In these formulas, the ligand s-orbital contributions, which were usually neglected in the previous studies, are taken into account based on the cluster approach. The ligand X− intervening in the Ni2+ and the next nearest neighbour Ag+ vacancy VAg is suggested to suffer a small inward displacement (≈ 0.11 or 0.15Å for AgCl or AgBr, respectively) towards Ni2+ along the [100] (or C4) axis. The calculated EPR parameters based on the above defect structures show reasonable agreement with the experimental data.

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