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2001 (3)
2000 (2)
1Author    Shao-Yi Wu, Wen-Chen ZhengRequires cookie*
 Title    Defect Structure of Co 2+ Center in 05-LiIO 3 Crystal  
 Abstract    In this paper we establish the formulas of EPR g factors g», for 3d 7 ions in trigonal octahedral crys-tals from a cluster approach. In these formulas, the contributions from configuration interaction-and covalency-effects are considered. The parameters related to both effects can be determined from the optical spectra and the structural parameters of the studied crystal. With these formulas, the defect struc-ture of a Co 2+ center in a-LiI0 3 crystal is studied. It is found that, to reach good fits between the cal-culated and observed g», g ± , the O ions between Co 2+ and Li + vacancy (V Li) should shift away from the V u by about 0.49 A. "Hie displacement direction is consistent with those obtained for Cr 3+ , Fe 3+ , and Mn 2 centers in a-LiI0 3 crystals as well as with the expectation based on the electrostatic interac-tion model. 
  Reference    Z. Naturforsch. 55a, 828—832 (2000); received June 29 2000 
  Published    2000 
  Keywords    Electron Paramagnetic Resonance (EPR), Crystal-field Theory, Defect Structure, Co 2+, a-LiI0 3 Crystal 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0828.pdf 
 Identifier    ZNA-2000-55a-0828 
 Volume    55 
2Author    Shao-Yi Wu, Wen-Chen ZhengRequires cookie*
 Title    Theoretical Studies of the g Factors for Co2+ in MgO and CaO Crystals  
 Abstract    This paper presents a cluster approach to the calculation of the g factors for 3d7 ions in cubic oc­ tahedral crystals, in which the parameters related to the configuration interaction and the covalency reduction effects are obtained from optical spectra of the studied crystals, and so no adjustable parameters are applied. From the approach, the g factors for MgO:Co2+ and CaO:Co2+ are cal­ culated. The calculated results show good agreement with the observed values. The experimental values of g < 4.333 (the first order value in absence of configuration and covalency interactions) for MgO:Co2+ and g > 4.333 for CaO:Co2+ are also explained. 
  Reference    Z. Naturforsch. 56a, 249—252 (2001); received October 13 2000 
  Published    2001 
  Keywords    Electron Paramagnetic Resonance (EPR), Crystal-field Theory, Co2+ Ion, MgO, CaO 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0249.pdf 
 Identifier    ZNA-2001-56a-0249 
 Volume    56 
3Author    W. Ua, Wen-Chen ZhengaRequires cookie*
 Title    Local Lattice Distortion near Co2+ in SrLaA104 Crystal  
 Abstract    The local tetragonal distortion in the vicinity of substitutional Co2+ impurities in SrLaA104 crystal is studied by fitting the calculated EPR parameters g\\, g±, A\\ and A± to the observed values. The result shows that the local distortion is mainly due to the elongation of metal-ligand distance R± perpendicular to the C 4 axis. This point is consistent with the expectation based on the consideration of ionic radius sum. This smaller tetragonal distortion of the oxygen octahedron surrounding the Co2+ impurity than that in the host crystal is supported by the result obtained in Cr3+-doped SrLaA104 crystal. -P a cs: 61.70Rj; 76.30Fc; 71.70Ch 
  Reference    Z. Naturforsch. 56a, 557—560 (2001); received May 11 2001 
  Published    2001 
  Keywords    Defect structure, Electronic Paramagnetic Resonance (EPR), Crystal Field Theory, SrLaA104 Crystal, Co2+ Ion 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0557.pdf 
 Identifier    ZNA-2001-56a-0557 
 Volume    56 
4Author    Wen-Chen Zheng, Shao-Yi WuRequires cookie*
 Title    Studies of the Local Phase-transition Behaviour for Ni + -II Centers in RbCaF 3 Crystal from EPR Data  
 Abstract    By fitting the calculated EPR g,(i = JC, y, z) factors to the observed values, the local release factor which is introduced to characterize the release (or elongation) effect of impurity-ligand bonds along the rotational axis in the cubic-to-tetragonal phase transition of ABX 3 perovskites, is obtained for the Ni + -II center in RbCaF 3 crystal. The result shows that, similar to the local rotational angle (or order param-eter) (p, the local release factor is unlike that of the host crystal. It suggests that in the doped crystal the impurity can affect the local phase transition behaviour in the vicinity of impurity ions. 
  Reference    Z. Naturforsch. 55a, 915—917 (2000); received September 12 2000 
  Published    2000 
  Keywords    Local Phase Transition Behaviour, E P R, Crystal-field Theory, Ni + ion, RbCaF 3 PACS: 6470Kb, 7630Fc, 7170Ch 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0915.pdf 
 Identifier    ZNA-2000-55a-0915 
 Volume    55 
5Author    Shao-Yi Wu, Wen-Chen ZhengRequires cookie*
 Title    Investigations of the EPR Parameters and Local Structures for Two Tetragonal Cr3* Centers in NH4C1 Crystal  
 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. 
  Reference    Z. Naturforsch. 56a, 326—3 (2001); received February 1 2001 
  Published    2001 
  Keywords    Spin-orbit Coupling, Electron Paramagnetic Resonance (EPR), Crystal-field Theory, Cr3+, NH4CI4 PACS: 7630Fc, 7170Ch 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0326.pdf 
 Identifier    ZNA-2001-56a-0326 
 Volume    56