共查询到17条相似文献,搜索用时 203 毫秒
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KCdF3晶体中Cr3+-Li+中心局域结构研究 总被引:2,自引:0,他引:2
利用零场分裂参量与晶体结构之间的定量关系,研究了双掺杂晶体KCdF3:Cr3+,Li+的局域结构。指出,对于KCdF3:Cr3+,Li+晶体,四角晶场的形成包含两个方面:(1)由于电荷补偿而产生的等效电荷形成的四角对称晶场;(2)Cr3+的局域结构发生晶格畸变而产生的四角对称晶场。事实上,当Cr3+和Li+掺入KCdF3晶体时,Cr3+代替了Cd2+离子;由于Cr3+离子与Cd2+离子的半径不同、电荷不同、质量不同,导致Cr3+的局域结构发生晶格畸变,由此而产生四角对称晶场;由于电荷补偿,Li+离子取代了[001]方向与Cr3+离子邻近的Cd2+离子,由此产生的等效电荷而形成的四角晶场。这样,Cr3+的局域结构由Oh对称变为C4v点对称。文中建立了ZFS参量和晶体结构之间的定量关系。在考虑晶格畸变和等效电荷的基础上,研究了KCdF3:Cr3+,Li+晶体的ZFS参量,理论结果和实验符合很好。得到了F-离子向中心离子分别移动为ΔR1=0.00268nm,ΔR2=0.001nm,ΔR3=0.00165nm。 相似文献
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RbMgF3 :Ni2+ 体系晶格局域结构的EPR理论研究 总被引:7,自引:2,他引:5
在考虑掺杂晶体局域畸变的影响后, 建立了联系RbMgF3: Ni2+体系的局域畸变结构与EPR谱间的关系, 并计算了RbMgF3: Ni2+晶体在C3v和D3d对称下的零场分裂参量和g 因数. EPR谱的理论计算值与实验值符合甚好. 相似文献
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掺杂晶体材料Al2O3∶Ni2+中顺磁离子N2+局域结构及其电子顺磁共振参量的研究 总被引:6,自引:0,他引:6
按照叠加模型和微扰理论,建立了电子顺磁共振(EPR)参量(D, g∥, g⊥)与Al2O3∶Ni2+晶体局域结构之间的定量关系. 利用EPR参量决定了Al2O3∶N i2+晶体的局域结构. 通过考虑适当的晶格畸变,成功地解释了Al2O3∶Ni2+晶体基态很大的零场分裂和各向异性的g因子. 获得了Ni2+ 离子上方最近邻的三个O2-离子偏向111〕晶轴0.603°, 而Ni2+离子下方的三个O2-离子偏向〔111〕晶轴0.598°. 相似文献
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利用零场分裂参量与晶体结构之间的定量关系,研究了双掺杂晶体KCdF3∶Cr3+,Li+的局域结构.指出,对于 KCdF3∶Cr3+,Li+晶体,四角晶场的形成包含两个方面:(1)由于电荷补偿而产生的等效电荷形成的四角对称晶场;(2)Cr3+的局域结构发生晶格畸变而产生的四角对称晶场.事实上,当Cr3+和Li+掺入KCdF3晶体时,Cr3+代替了Cd2+离子;由于Cr3+离子与Cd2+离子的半径不同、电荷不同、质量不同,导致Cr3O+的局域结构发生晶格畸变,由此而产生四角对称晶场;由于电荷补偿,Li+ 离子取代了[001]方向与Cr3+离子邻近的Cd2+离子,由此产生的等效电荷而形成的四角晶场.这样,Cr3+的局域结构由Oh对称变为C4v点对称 .文中建立了ZFS参量和晶体结构之间的定量关系.在考虑晶格畸变和等效电荷的基础上,研究了KCd F 3∶Cr3+,Li+晶体的ZFS参量,理论结果和实验符合很好.得到了F-离子向中心离子分别移动为ΔR1=0.00268nm,ΔR2=0.001nm,ΔR3=0.00165nm . 相似文献
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在统一配体场耦合图像的基础上,构造了d4电子组态过渡金属离子在强场图像下包括所有自旋状态的210×210维完全能量矩阵.通过对角化完全能量矩阵,研究了Cr2+掺杂ZnS的局域晶格结构和Jahn-Teller能.理论计算结果与实验值符合非常好.同时,还研究了Cr2+掺杂ZnS后体系自旋单态对零场分裂参量的贡献.结果表明:自旋单态对二阶零场分裂参量D的贡献可以忽略,但是对于四阶零场分裂参量a和F的贡献却
关键词:
2+')" href="#">ZnS:Cr2+
统一配体场耦合
自旋单态
Jahn-Teller能 相似文献
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基于配位场理论,建立d3组态离子在三角晶场中的完全能量矩阵,采用完全能量矩阵的对角化计算方法,研究了绿宝石晶体Cr3+:Be3Al2(SiO3)6的光谱和EPR谱,理论值与实验值符合得很好.通过分析绿宝石晶体中(CrO6)9-团簇的光谱和EPR谱,研究了配体在络合物中的极化现象.结果表明由于周围配位环境的影响,绿宝石晶体中(CrO<
关键词:
3+:Be3Al2(SiO3)6体系')" href="#">Cr3+:Be3Al2(SiO3)6体系
光谱
EPR谱
局域结构极化 相似文献
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Local structure distortion and spin Hamiltonian parameters for Cr3+-Vzn tetragonal defect centre in Cr3+ doped KZnF3 crystal 下载免费PDF全文
The quantitative relationship between the spin Hamiltonian parameters (D, g‖, Δg) and the crystal structure parameters for the Cr3+—VZn tetragonal defect centre in a Cr3+:KZnF3 crystal is established by using the superposition model. On the above basis, the local structure distortion and the spin Hamiltonian parameter for the Cr3+—VZn tetragonal defect centre in the KZnF_3 crystal are systematically investigated using the complete diagonalization method. It is found that the VZn vacancy and the differences in mass, radius and charge between the Cr3+ and the Zn2+ ions induce the local lattice distortion of the Cr3+ centre ions in the KZnF3 crystal. The local lattice distortion is shown to give rise to the tetragonal crystal field, which in turn results in the tetragonal zero-field splitting parameter D and the anisotropic g factor Δg. We find that the ligand F- ion along [001] and the other five F- ions move towards the central Cr3+ by distances of Δ1 = 0.0121 nm and Δ2 = 0.0026 nm, respectively. Our approach takes into account the spin—orbit interaction as well as the spin—spin, spin—other-orbit, and orbit—orbit interactions omitted in the previous studies. It is found that for the Cr3+ ions in the Cr3+:KZnF3 crystal, although the spin—orbit mechanism is the most important one, the contribution to the spin Hamiltonian parameters from the other three mechanisms, including spin—spin, spin—other-orbit, and orbit—orbit magnetic interactions, is appreciable and should not be omitted, especially for the zero-field splitting (ZFS) parameter D. 相似文献
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AN INVESTIGATION FOR THE Cd2+-VACANCIES IN RbCdF3 and CsCdF3 CRYSTALS DOPED WITH Fe3+ IMPURITIES 下载免费PDF全文
余万伦 《物理学报(海外版)》1993,2(8):610-618
This paper presents high-order perturbation calculations for the zero-field splitting parameters D, F, and a of Fe3+-VCd pairs in RbCdF3 and CsCdF3 crystals doped with Fe3+ impurities. In comparison with experimental data, the present results are better than those obtained in previous work by using the phenomenological su-perposition model of spin-Hamiltonian. Moreover, the crystal fields arising from the Cd2+-vacancy and their induced crystal lattice distortion are analysed and calculated. It is found that the contribution from the Cd2+-vacancies cannot be ignored. Mena-while, we obtain that a ligand F- along the [001]-axis moves towards the central Fe3+ ion by Δ= 0.0020nm in RbCdF3 and 0.0028nm in CsCdF3. These results are quite different from Δ = 0.0104nm and Δ = 0.0112nm, respectively, obtained in previous work by using the superposition model of spin-Hamiltonian and ignoring the effect of the vacancy. 相似文献
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YAG∶Cr3+ 晶体精细光谱结构研究 总被引:6,自引:3,他引:3
采用不同的晶体畸变模型,利用CDM(complete diagonalization method)方法对YAG∶Cr3+ 晶体的EPR参量进行了系统研究.通过计算结果对晶格畸变模型进行了分析.结果表明,在三角对称下,对杂质离子电荷与中心离子电荷相等的情况,不适合用杂质离子沿C3轴位移的模型来研究晶体的局域结构,而且由于基态和第一激发态的零场分裂都对局域结构微变非常敏感,因此仅由基态零场分裂来确定晶格局域结构是不可靠的.同时结果表明,Cr3+ 离子进入YAG晶体后,产生了Δθ=1.88°的三角畸变.从而成功统一地解释了YAG∶Cr3+ 晶体的EPR参量和精细光谱结构. 相似文献
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Z. -Y. Yang 《Applied magnetic resonance》2000,18(4):455-461
In this paper, the electron paramagnetic resonance (EPR) parameters in RbCdF3:Cr3+ have been studied by means of energy matrices and the Newman superposition model, the theoretical results are in excellent agreement with the experimental ones. The existence of Rb+ vacancy and the lattice distortion have been verified. The EPR parameters arising from the Rb+ vacancy itself and the crystal lattice distortion are analyzed and calculated. We obtain that the six ligand F− ions move to the central Cr3+ ion by Δ = 0.0013 nm, and the front three F− ions rotate 2.98° away from the [111] axis while the back three F− ions rotate 1.016° toward it. 相似文献
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《Journal of magnetism and magnetic materials》2002,238(2-3):200-206
The quantitative relationship between the electron paramagnetic resonance (EPR) parameters D,g∥,g⊥ and the local structure parameters of Cr3+ ion in KZnF3 crystals is established. The local structure for Cr3+ paramagnetic center in KZnF3:Cr3+ crystal has been determined from EPR parameters of Cr3+ ion. This work shows that the trigonal crystal field of Cr3+ ion in KZnF3 crystals comes from following two origins: (1) the nearest-neighbor K+ vacancy caused by the charge compensation in the [1 1 1]-axis direction; and (2) the lattice distortions of the nearest-neighbor fluorine coordination caused by the K+ vacancy and the differences in mass, charge, and radius between Cr3+ ion and Zn2+ ion. The unified calculation of the EPR zero-field splitting and g factors, taking into account the K+ vacancy and the lattice distortions, has been carried out on the basis of the complete diagonalization procedure and the superposition crystal-field model, all calculation results are in excellent agreement with the experimental data. Although the main source of the trigonal crystal field comes from the K+ vacancy caused by the charge compensation, the contribution of the lattice distortion cannot be neglected. 相似文献
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V. Lavrentiev J. Vacik A. Dejneka V. Trepakov L. Jastrabik 《Physics of the Solid State》2013,55(7):1431-1437
The results of ion channeling studies of lattice distortions in SrTiO3: Cr single crystals are presented. Two types of single crystals containing the same amount of Cr impurities but differing in stoichiometry have been investigated. The single crystals grown by the Verneuil method have the compositions of standard-grown SrTiO3: Cr (0.05 at % Cr), whereas the single crystals grown with a strontium deficiency and a chromium compensating amount have the composition Sr0.9995TiO3 (0.05 at % Cr). Analysis of the angular channeling spectra indicates that, in crystals of both types, the main defects are Cr impurities located in octahedral sites. In the SrTiO3: Cr crystals, impurity atoms manifest themselves as Cr4+ with tetragonal Jahn-Teller distortions of the surrounding lattice. In the Sr0.9995TiO3: Cr crystals grown with a Sr deficiency, the characteristic displacements of Ti ions in the third coordination sphere of the Jahn-Teller center Cr4+ exhibit the effect of interaction of the center with a neighboring vacancy in the Sr sublattice. 相似文献