低對稱場中3d~9離子自旋哈密頓參量的理論研究
發(fā)布時間：2019-06-06 20:15
【摘要】：很多摻雜3d9(Cu2+)離子的功能材料具有奇異的磁性、催化、導電、非線性光學性質和自組裝結構特性而引起研究者的關注。這些材料的光學和磁學性質敏感地取決于其中摻雜的過渡離子(如Cu2+)周圍的局部環(huán)境,而且可借助電子順磁共振(EPR)譜學手段進行研究。針對3d9離子這一過渡族中非常重要的體系,前人的EPR研究積累了豐富的實驗數據,并描述為自旋哈密頓參量(各向異性g因子和超精細結構常數等)。遺憾的是,以前的研究者對于上述實驗結果進行理論分析時存在一些缺陷,例如大多是建立于傳統晶體場模型并且忽略了配體旋-軌耦合的貢獻,沒有將理論分析和雜質中心的局部結構相聯系等。為了克服上述不足,本文在考慮配體貢獻的基礎上,得到了3d9離子在四角和斜方(正交)拉伸八面體中關于自旋哈密頓參量(g因子和A因子)的高階微擾公式,并建立了晶場參量和歸一化因子等參量與體系光譜實驗數據和局部結構信息的關系。將上述公式應用于以下低對稱3d9體系,滿意地解釋了EPR實驗結果。1)對于NaCl和AgCl中的四角Cu2+中心,基于考慮配體軌道和旋軌耦合貢獻的改進離子簇模型的(g因子和A因子)的高階微擾公式就算得到的理論值與實驗結果符合的很好,并且發(fā)現雜質中心由于Jahn-Teller效應而沿C4軸發(fā)生約0.15和0.08?相對四角伸長。雖然配體氯的旋軌耦合系數比中心離子銅的略小,但由于體系有明顯的共價性而導致配體貢獻較重要而不能被忽略。2)對于氧化和非氧化的BaCuO2+x中的正交Cu2+位置,由于Jahn-Teller效應引起[CuO6]10?基團沿c軸方向分別發(fā)生了1%和0.6%的相對伸長,而垂直方向的平面鍵長則分別發(fā)生有6.9%和8.9%的相對變化。上述的局部正交畸變分別對應于實驗測得的軸向和垂向g因子各向異性。本工作的研究將有助于理解寄生相Ba CuO2+x的EPR行為及其對母體R123高溫超導體相關譜學性質和超導電性的影響。3)合理解釋了[Cu(ipt)(dap)H2O]n?nH2O中斜方Cu2+位置的自旋哈密頓參量。EPR實驗測到的近軸各向異性g因子和超精細結構常數可歸因于顯著拉伸的五角錐[CuN2O3]基團,而輕微的垂向各向異性則源于不同平面配體N和O,其貢獻可能在很大程度上互相抵消,從而導致實驗誤差范圍內近軸的EPR信號。上述分析對于理解[Cu(ipt)(dap)H2O]n?nH2O及類似體系的局部結構和譜學性質具有參考價值。4)合理解釋了[Cu(men)2(BF4)2](men=N-methyl-1,2-diaminoethane)中斜方Cu2+的各向異性g因子。基于斜方伸長八面體中3d9離子g因子高階微擾公式的理論值與實驗結果符合的較好。銅離子所處的六配位[CuN4F2]基團表現出明顯的斜方伸長畸變。由于Cu2+-N3?鍵長較短而使體系具有很強的共價性,故在EPR分析時配體軌道和自旋-軌道耦合的貢獻應當予以考慮。
[Abstract]:Many functional materials doped with 3d9 (Cu2) ions have attracted the attention of researchers because of their strange magnetic, catalytic, conductive, nonlinear optical properties and self-assembly structural properties. The optical and magnetic properties of these materials are sensitive to the local environment around the doped transition ions, such as Cu2, and can be studied by electron parammagnetic resonance (EPR) spectroscopy. For 3d9 ion, which is a very important system in the transition family, the previous EPR studies have accumulated a wealth of experimental data and described them as spin Hamilton parameters (anisotropy g factor and hyperfine structure constant, etc.). Unfortunately, previous researchers have some defects in the theoretical analysis of the above experimental results, for example, most of them are based on the traditional crystal field model and ignore the contribution of ligand rotation-orbit coupling. The theoretical analysis is not related to the local structure of the impurity center. In order to overcome the above shortcomings, on the basis of considering the contribution of ligands, the higher order perturbation formulas of spin Hamilton parameters (g factor and A factor) for 3d9 ions in tetrahedral and oblique (orthogonal) tensile octahedral are obtained in this paper. The relationship between the parameters such as crystal field parameters and normalization factors and the experimental data and local structure information of the system is established. The above formulas are applied to the following low symmetric 3d9 systems, and the experimental results of EPR are explained with satisfaction. 1) for the quadrangle Cu2 centers in NaCl and AgCl, Based on the higher order perturbation formula of the improved ion cluster model (g factor and A factor) considering the contribution of ligand orbital and rotating orbit coupling, the theoretical values obtained are in good agreement with the experimental results. It is found that the impurity center occurs about 0. 15 and 0. 08 along the C 4 axis because of the Jahn-Teller effect. The relative four corners stretch. Although the spin-orbit coupling coefficient of ligand chlorine is slightly smaller than that of central ion copper, the ligand contribution is important and can not be ignored because of the obvious covalent property of the system. 2) for the orthogonal Cu2 position in oxidized and non-oxidized BaCuO2 x, [CuO6] 10? caused by Jahn-Teller effect? The relative extension of the group along the c axis was 1% and 0.6%, respectively, while the plane bond length in the vertical direction changed by 6.9% and 8.9%, respectively. The above local orthonormal distortion corresponds to the axial and vertical g factor anisotropy measured by experiments, respectively. The study of this work will be helpful to understand the EPR behavior of parasitic phase Ba CuO2 x and its effect on the related spectral properties and superconductivity of parent R123 high temperature superconductor. 3) the skew in [Cu (ipt) (dap) H2O] n?nH2O is explained reasonably. The spin Hamilton parameters of square copper position. The paraxial anisotropy g factor and hyperfine structure constant measured by EPR can be attributed to the significantly stretched pentagonal cone [CuN2O3] group. The slight vertical anisotropy originates from different plane ligands N and O, and their contributions may cancel each other to a large extent, resulting in paraxial EPR signals in the experimental error range. The above analysis has reference value for understanding the local structure and spectral properties of [Cu (ipt) (dap) H2O] n?nH2O and similar systems. 4) the reasonable explanation of [Cu (men) 2 (BF4) 2] (men=N-methyl-1,2-diaminoethane) The anisotropy g factor of Cu2 in the middle oblique square. The theoretical values based on the higher order perturbation formula of 3d9 ion g factor in oblique elongated octahedral are in good agreement with the experimental results. The six coordination [CuN4F2] groups in which copper ions are located show obvious oblique extension distortion. Because of Cu2-N3? The short bond length makes the system have strong covalency, so the contribution of ligand orbital and spin-orbit coupling should be considered in EPR analysis.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TB34
本文編號：2494567
[Abstract]:Many functional materials doped with 3d9 (Cu2) ions have attracted the attention of researchers because of their strange magnetic, catalytic, conductive, nonlinear optical properties and self-assembly structural properties. The optical and magnetic properties of these materials are sensitive to the local environment around the doped transition ions, such as Cu2, and can be studied by electron parammagnetic resonance (EPR) spectroscopy. For 3d9 ion, which is a very important system in the transition family, the previous EPR studies have accumulated a wealth of experimental data and described them as spin Hamilton parameters (anisotropy g factor and hyperfine structure constant, etc.). Unfortunately, previous researchers have some defects in the theoretical analysis of the above experimental results, for example, most of them are based on the traditional crystal field model and ignore the contribution of ligand rotation-orbit coupling. The theoretical analysis is not related to the local structure of the impurity center. In order to overcome the above shortcomings, on the basis of considering the contribution of ligands, the higher order perturbation formulas of spin Hamilton parameters (g factor and A factor) for 3d9 ions in tetrahedral and oblique (orthogonal) tensile octahedral are obtained in this paper. The relationship between the parameters such as crystal field parameters and normalization factors and the experimental data and local structure information of the system is established. The above formulas are applied to the following low symmetric 3d9 systems, and the experimental results of EPR are explained with satisfaction. 1) for the quadrangle Cu2 centers in NaCl and AgCl, Based on the higher order perturbation formula of the improved ion cluster model (g factor and A factor) considering the contribution of ligand orbital and rotating orbit coupling, the theoretical values obtained are in good agreement with the experimental results. It is found that the impurity center occurs about 0. 15 and 0. 08 along the C 4 axis because of the Jahn-Teller effect. The relative four corners stretch. Although the spin-orbit coupling coefficient of ligand chlorine is slightly smaller than that of central ion copper, the ligand contribution is important and can not be ignored because of the obvious covalent property of the system. 2) for the orthogonal Cu2 position in oxidized and non-oxidized BaCuO2 x, [CuO6] 10? caused by Jahn-Teller effect? The relative extension of the group along the c axis was 1% and 0.6%, respectively, while the plane bond length in the vertical direction changed by 6.9% and 8.9%, respectively. The above local orthonormal distortion corresponds to the axial and vertical g factor anisotropy measured by experiments, respectively. The study of this work will be helpful to understand the EPR behavior of parasitic phase Ba CuO2 x and its effect on the related spectral properties and superconductivity of parent R123 high temperature superconductor. 3) the skew in [Cu (ipt) (dap) H2O] n?nH2O is explained reasonably. The spin Hamilton parameters of square copper position. The paraxial anisotropy g factor and hyperfine structure constant measured by EPR can be attributed to the significantly stretched pentagonal cone [CuN2O3] group. The slight vertical anisotropy originates from different plane ligands N and O, and their contributions may cancel each other to a large extent, resulting in paraxial EPR signals in the experimental error range. The above analysis has reference value for understanding the local structure and spectral properties of [Cu (ipt) (dap) H2O] n?nH2O and similar systems. 4) the reasonable explanation of [Cu (men) 2 (BF4) 2] (men=N-methyl-1,2-diaminoethane) The anisotropy g factor of Cu2 in the middle oblique square. The theoretical values based on the higher order perturbation formula of 3d9 ion g factor in oblique elongated octahedral are in good agreement with the experimental results. The six coordination [CuN4F2] groups in which copper ions are located show obvious oblique extension distortion. Because of Cu2-N3? The short bond length makes the system have strong covalency, so the contribution of ligand orbital and spin-orbit coupling should be considered in EPR analysis.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TB34
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