低对称场中3d~9离子自旋哈密顿参量的理论研究
发布时间：2019-06-06 20:15
【摘要】：很多掺杂3d9(Cu2+)离子的功能材料具有奇异的磁性、催化、导电、非线性光学性质和自组装结构特性而引起研究者的关注。这些材料的光学和磁学性质敏感地取决于其中掺杂的过渡离子(如Cu2+)周围的局部环境,而且可借助电子顺磁共振(EPR)谱学手段进行研究。针对3d9离子这一过渡族中非常重要的体系,前人的EPR研究积累了丰富的实验数据,并描述为自旋哈密顿参量(各向异性g因子和超精细结构常数等)。遗憾的是,以前的研究者对于上述实验结果进行理论分析时存在一些缺陷,例如大多是建立于传统晶体场模型并且忽略了配体旋-轨耦合的贡献,没有将理论分析和杂质中心的局部结构相联系等。为了克服上述不足,本文在考虑配体贡献的基础上,得到了3d9离子在四角和斜方(正交)拉伸八面体中关于自旋哈密顿参量(g因子和A因子)的高阶微扰公式,并建立了晶场参量和归一化因子等参量与体系光谱实验数据和局部结构信息的关系。将上述公式应用于以下低对称3d9体系,满意地解释了EPR实验结果。1)对于NaCl和AgCl中的四角Cu2+中心,基于考虑配体轨道和旋轨耦合贡献的改进离子簇模型的(g因子和A因子)的高阶微扰公式就算得到的理论值与实验结果符合的很好,并且发现杂质中心由于Jahn-Teller效应而沿C4轴发生约0.15和0.08?相对四角伸长。虽然配体氯的旋轨耦合系数比中心离子铜的略小,但由于体系有明显的共价性而导致配体贡献较重要而不能被忽略。2)对于氧化和非氧化的BaCuO2+x中的正交Cu2+位置,由于Jahn-Teller效应引起[CuO6]10?基团沿c轴方向分别发生了1%和0.6%的相对伸长,而垂直方向的平面键长则分别发生有6.9%和8.9%的相对变化。上述的局部正交畸变分别对应于实验测得的轴向和垂向g因子各向异性。本工作的研究将有助于理解寄生相Ba CuO2+x的EPR行为及其对母体R123高温超导体相关谱学性质和超导电性的影响。3)合理解释了[Cu(ipt)(dap)H2O]n?nH2O中斜方Cu2+位置的自旋哈密顿参量。EPR实验测到的近轴各向异性g因子和超精细结构常数可归因于显著拉伸的五角锥[CuN2O3]基团,而轻微的垂向各向异性则源于不同平面配体N和O,其贡献可能在很大程度上互相抵消,从而导致实验误差范围内近轴的EPR信号。上述分析对于理解[Cu(ipt)(dap)H2O]n?nH2O及类似体系的局部结构和谱学性质具有参考价值。4)合理解释了[Cu(men)2(BF4)2](men=N-methyl-1,2-diaminoethane)中斜方Cu2+的各向异性g因子。基于斜方伸长八面体中3d9离子g因子高阶微扰公式的理论值与实验结果符合的较好。铜离子所处的六配位[CuN4F2]基团表现出明显的斜方伸长畸变。由于Cu2+-N3?键长较短而使体系具有很强的共价性,故在EPR分析时配体轨道和自旋-轨道耦合的贡献应当予以考虑。
[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.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB34
本文编号：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.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB34
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