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1.
杨子元 《物理学报》2014,63(17):177501-177501
基于Newman的晶场叠模型与微观自旋哈密顿理论,建立了ZnGa2O4:Fe3+晶体材料中磁性离子Fe3+局域结构与其自旋哈密顿(spin-Hamiltonian,SH)参量(包括二阶零场分裂(zero-field splitting,ZFS)参量D,四阶ZFS参量(a-F),Zeeman g因子:g//,g⊥,△g(=g//-g⊥))之间的定量关系.采用以全组态完全对角化方法为理论背景的CFA/MSH(Crystal Filed Analysis/Microscopic Spin Hamiltonian)研究软件,研究了ZnGa2O4:Fe3+材料中磁性离子Fe3+的SH参量与其局域结构的依赖关系.研究表明:对于ZnGa2O4:Fe3+晶体材料,当磁性离子Fe3+的局域结构畸变参数△R=0.0487 nm,△θ=0.192°时,其基态SH参量理论计算结果与实验测量符合很好,进一步表明Fe3+掺入晶体材料后将引起磁性Fe3+离子局域结构的微小畸变,但其仍然保持D3d点群对称局域结构.在此基础上研究分析了SH参量的微观起源,结果表明:ZnGa2O4:Fe3+晶体材料的SH参量主要来源于SO(spin-orbit)磁相互作用机理,来自其他磁相互作用机理(包括SS(spin-spin),SOO(spin-other-orbit),OO(orbit-orbit),SO-SS-SOO-OO)的贡献比较小.  相似文献   

2.
杨子元 《波谱学杂志》2001,18(3):209-214
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   

3.
The g factors g||,g⊥ and hyperfine structure constants A||,A⊥ for two trigonal Co^2 centers (i.e.,Co^2 in Cd^2 (I) and Cd^2 (Ⅱ) sites) in CsCdCl3:Co^2 crystals are calculated from the high-order perturbation formulas based on the cluster approach.In the calculation,the contributions from covalency effect and configuration interaction effect are considered and the parameters related to both effects are obtained from the optical spectrum and the structure data of the studied system.The results are in good agreement with the observed values.  相似文献   

4.
In this paper, the high-order perturbation formulas of spin-Hamiltonian (SH) parameters (g factors g, g and zero-field splitting D), including both the crystal-field (CF) and for the first time charge-transfer (CT) mechanisms, are established for 3d8 ions in trigonal octahedral clusters. By using these formulas, the SH parameters of Ni2+ ions in CsMgX3 (X=Cl, Br, I) crystals are calculated. The results are consistent with the experimental values. The calculations suggest that the sign of QCT (Qg, Δg or D, where the g-shift Δgi=gige, ge≈2.0023 is the value of free-electron) due to CT mechanism is the same as that of the corresponding QCF due to CF mechanism, and the relative importance of CT mechanism (characterized by QCT/QCF) increases with the increasing atomic number of ligand X. So, for the 3dn MLm clusters with ligand having large atomic number, the reasonable theoretical explanations of all SH parameters should take both CF and CT mechanisms into account. The defect structure of (NiX6)4− impurity centers in CsMgX3:Ni2+ crystals is also considered in our model.  相似文献   

5.
The high-order perturbation formulas of electron paramagnetic resonance (EPR) parameters (g factors g∥,g and zero-field splitting D) for 3d8 ions in trigonal octahedral clusters are established. These formulas contain the contributions not only from the crystal-field (CF) mechanism, but also from the charge-transfer (CT) mechanism (which is not considered in the widely used CF theory). From these formulas, the EPR parameters and the impurity-induced defect structures for Ni2+ ions in CdX2 (X=Cl, Br) crystals are studied. The calculated EPR parameters are coincident with the experimental values, and the defect structure of Ni2+ impurity center obtained from the calculation is different from the corresponding structure in the host crystal. The sign of QCT (Qg, Δg, or D) due to CT mechanism agrees with that of the corresponding QCF due to CF mechanism and the relative importance of CT mechanism (characterized by QCT/QCF) increases with increasing covalence of 3d8 clusters and hence with raising atomic number of ligand X. So, in the explanations of the EPR parameters of 3d8 (or other 3dn) ions in crystals with the heavy-element ligand ion (e.g., Br), the calculated formulas based on the two-mechanism (CF and CT mechanisms) model are preferable to those based on only the CF mechanism in the CF theory.  相似文献   

6.
采用微扰方法和对角化完全能量矩阵法计算了Al2O3粉末吸附的四角对称[Cu(H2O)6]2+基团的自旋哈密顿参量(g因子g∥,g和超精细结构常数A和A). 计算结果表明用这两种理论方法计算的自旋哈密顿参量很接近,并且都与实验结果比较一致. 表明这2种方法都可用于晶体中3d9离子基团的自旋哈密顿参量的研究,通过计算,我们还获得了[Cu(H2O)6]2+基团四角畸变的大小,并对结果进行了讨论.  相似文献   

7.
Complete high-order perturbation formulas are established based on charge-transfer (CT) and crystal-field (CF) mechanisms. The electron paramagnetic resonance (EPR) g-factors of MgTiO3:Cr3+, SrTiO3:Cr3+, and SrTiO3:Mn4+ crystals are calculated from the formulas. The calculations of the EPR g-factors agree well with the experimental values. The contribution rate of the CT mechanism to EPR parameters increases with increasing valence state of the 3d n ions in the crystals. For the higher-valence state 3d 3 Mn4+ ion in the crystals, the elucidation of the EPR parameters rationally involves both CF and CT mechanisms.  相似文献   

8.
With the strong-field scheme and trigonal bases, by diagonalizing the complete d3 energy matrix in a trigonally distorted cubic-field, the energy spectra and wavefunctions of YAl3(BO3)4:Cr3+ have been calculated. The rates of change of levels with respect to various parameters and the contributions to levels from various parameters are calculated, and the physical origins of various levels or splittings have been clearly and quantitatively shown. By using the wavefunctions obtained from diagonalizing the complete energy matrix, the g factors of the ground state of YAl3(BO3)4:Cr3+ have been evaluated. The calculated results are in good agreement with the optical-spectral and EPR experimental data. It is demonstrated that the bonding between Cr3+ and ligands (O2-) is ionic.  相似文献   

9.
本文考虑到d8电子组态中所有自旋三重态和自旋单态对基态的影响,用高阶微扰法导出了d8电子组态在三角对称晶场下光谱和基态EPR普遍公式。发现在三角对称晶场下,d8电子组态离子的g > gg < gD > 0或D < 0是以立方对称晶场为界,晶体中顺磁离子的配体沿C3轴伸长或压缩所致。利用所得公式计算了NiCl2和NiSiF6·6H2O晶体的EPR参量,其结果与实验吻合较好。  相似文献   

10.
Photoluminescence (PL), photostimulated luminescence (PSL), thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were carried out on LiYF4:U4+ and pure LiYF4 crystals. The PL and EPR investigations have identified the presence of Eu3+, Tb3+ and Gd3+ ions in both of these crystals possibly due to their existence in the starting materials. The luminescence observed during afterglow, PSL and TSL revealed that emission occurs at wavelength positions 382, 413, 437 and 544 nm, which are characteristic of Tb3+ ions. The present investigations using PSL and TSL in combination with PL studies before and after gamma irradiation have revealed that selective energy transfer to Tb3+ ions occurs during electron–hole recombination processes like PSL and TSL. Even though other luminescent ions (U4+ and Eu3+) are present in the system and U4+/U3+ ions are participating in electron capture/release processes, the selective energy transfer results in Tb3+ ions acting as luminescence centers.  相似文献   

11.
The electron paramagnetic resonance (EPR) properties of the Mn2+ ions in PbWO4 single crystals grown by the Czochralski method have been investigated in the X-band microwave frequency, at T=20 K. The angular dependence of the EPR line positions obtained by rotating the magnetic field in the main crystallographic planes shows that the local symmetry at the Mn2+ impurity ions is tetragonal, strongly suggesting that the Mn2+ ions substitute for the Pb2+ lattice cations, without charge compensation. The resulting spin Hamiltonian parameters compare well with the corresponding values for the Mn2+ ions in other isomorphous tungstates. The observed strong angular variation of the EPR linewidth has been quantitatively described considering a random distribution of lattice strains.  相似文献   

12.
文章考察了Mo-SiO2催化剂体系在丙烯歧化反应过程中的动态ESR波谱,发现在催化歧化反应过程中有两种Mo5+顺磁中心,一种为扰动八面体配位,g||=1.89,g=1.94;另一种为扰动四棱锥配位,g||=1.86,g=1.95。测得同位素95,97Mo5+的各向异性超精细耦合常数A||=90.3×10-4cm-1,A=44.8×10-4cm-1;观测到反应产生的积炭信号,g≈2.0O2;氧阴离子自由基信号g1=2.018,g2=2.011,g3=2.005。用LCAO-MO理论对上述Mo5+的ESR波谱进行计算,求得分子轨道系数,发现并总结出△g||/△g与△g成直线关系,并建议用△g||/△g=4(△E(B2→E))/(△E(B2→B1)(β1/ε)2之比值作为衡量C4v扰动程度的尺度。  相似文献   

13.
The EPR 9 factors for cubic, tetragonal and orthorhombic Fe^+ centers in alkali halides MX (M= Li, Na; X = F, CI) are calculated from second-order perturbation formulas of g factors based on cluster approach for 3d^7 ions in three symmetries. From calculations, the g factors of these Fe^+ centers in MX crystals are reasonably explained and the defect structural data for the tetragonal and orthorhombic Fe^+ centers are estimated. The results are discussed.  相似文献   

14.
沙昆源  冷晶 《波谱学杂志》1992,9(3):263-267
对掺Cr3+乙酰丙酮铝单晶的(001),(100)和(110)晶面进行晶面旋转EPR扫描,得到共振磁场随旋转角度变化的实验图形,根据本征插方法编写的程序,对实验谱图进行投合,得到下述顺磁参数,D=0.5870±O.005cm-1,E=-0.00490±0.0001cm-1,gx=gy=1.965±0.001,g2=1.984±0.001.  相似文献   

15.
A new EPR spectrum in YBCO single crystals doped by Al3+ ions have been revealed. The spectrum was assigned to trivalent Cu3+ (S=1) ions in the Cu(1) position and the spin-hamiltonian parameters describing the observed spectrum have been determined on the basis of computer calculation of the EPR spectrum. The theoretical consideration and numerical estimations carried out showed that the ground state of Cu3+ ions in the YBCO system might be a triplet and, thus, the possibility of the observation of its EPR spectrum has been confirmed. The analysis of the experimentally determined g-factor values showed the important role of the hybridization of 3d-copper and 2p-oxygen states and, in particular, the significant contribution of the Cu2+-O- state in the ground one. The stabilization of Cu3+ states in YBCO single crystals by Al3+ ions is discussed. It is shown that the observed temperature dependence of the gx-value was due to the displacement of the apex oxygen O(4) in the direction of the CuO2 plane as TTc.  相似文献   

16.
With the strong-field scheme and cubic bases,the complete d^3 energy matrix in a tetragonally distorted cubic-field has been constructed.By diagonalizing this matrix,the energy spectra of SrTiO3:Cr^3 and SrTiO3:Mn^4 at normal pressure and various temperatures have been calculated.Correspondingly,the FORTRAN program calculating the g factor of the ground state has been worked out.By using the program and the wavefunction obtained from diagonalizing the complete energy matrix,the g factors of the ground state of SrTiO3:Cr^3 and SrTiO3:Mn^4 at normal pressure and room temperature have been evaluated.The calculated results are in good agreement with the optical-spectral and EPR experimental data.The comparison and analysis of the results of two crystals have been made.It is demonstrated that the covalency of the bonding between Mn^4 and ligands(O^2-) in SrTiO3:Mn^4 is stronger than the one of the bonding between Cr^3 and ligands(O^2-)in SrTiO3:Cr^3 .It is shown that the obtained wavefunctions and values of parameters are reasonable.  相似文献   

17.
在化学计量的熔料里,用提拉法生长了K5Bi0.9Nd0.1(MoO4)4和K5Bi0.97Nd0.03(MoO4)4单晶。该晶体属于三方晶系,空间群为R3m,Z=1.5,晶胞常数为a=6.023?,c=20.887?(Nd0.1)。K5Bi(Mo 关键词:  相似文献   

18.
The influence of Fe and Li co-doping on optical properties of ZnWO4 crystals have been investigated by optical spectroscopy and electron paramagnetic resonance (EPR). The iron ions were added to the ZnWO4 composition in the form of Fe0, FeO or Fe2O3. EPR has been used for determination of the Fe3+ concentration. The luminescence and excitation spectra obtained at different temperatures are presented. Under excitation 325 nm, two bands were observed: blue-green emission peaked at 490 nm and red peaked at 650 nm. The blue- green emission is related to Fe3+ and their shape depends on the doping method. The red emission is not related to the Fe3+.  相似文献   

19.
The dominant Ti3+ trapped electron center in flux-grown RbTiOPO4 (RTP) crystals has been characterized using electron paramagnetic resonance (EPR) and electron–nuclear double resonance (ENDOR). This center is produced during an X-ray irradiation at room temperature when a Ti4+ ion traps an electron and becomes a Ti3+ ion, and is best studied in the 30–40 K range. The EPR spectrum contains a three-line hyperfine pattern from two nearly equivalent neighboring 31P nuclei, along with hyperfine lines from the 47Ti and 49Ti nuclei. The g matrix, determined from the angular dependence of the EPR spectrum, has principal values of 1.819, 1.889, and 1.947. Hyperfine matrices for four 31P nuclei are obtained from the angular dependence of the ENDOR spectrum. The proposed model for this defect is a Ti3+ ion adjacent to an oxygen vacancy at an OT position. Analogies are made to a similar Ti3+ center in KTiOPO4 (KTP) crystals.  相似文献   

20.
Traditional ligand-field theory has to be improved by taking into account both “pure electronic” contribution and electron-phonon interaction one (including lattice-vibrational relaxation energy). By means of improved ligand-field theory, R1, R2, R'3, R'2, and R'1 lines, U band, ground-state zero-field-splitting (GSZFS) and ground-state g factors as well as thermal shifts of R1 line and R2 line of YAG:Cr3+ have been calculated. The results are in very good agreement with the experimental data. In contrast with ruby, the octahedron of ligand oxygen ions surrounding the central Cr3+ ion in YAG:Cr3+ is compressed along the [111] direction. Thus, for YAG:Cr3+ and ruby, the splitting of t234A2 (or t232E) has opposite order, and the trigonal-field parameters of the two crystals have opposite signs. In thermal shifts of R1 and R2 lines of YAG:Cr3+, the temperature-dependent contributions due to EPI are dominant.  相似文献   

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