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1.
In this paper, the optical absorption and electron spin resonance (ESR) spectrum of Ni+‐doped CuAlS2 crystals have been studied by using a double spin‐orbit (SO) coupling approximation model, where the effects due to the SO coupling of the central metal 3d1 ion and those of ligands are included. From this model, the formulas of the ESR g factors g‖, g⊥ and hyperfine structure constants A‖, A⊥ for 3d1 ions in the tetragonal MX4 clusters are constructed. The optical absorption and ESR parameters for Cu+ sites of CuAlS2 have been calculated. The results obtained show that Ni+ ions substitute for Cu+ ions sites. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
2.
The spin‐Hamiltonian parameters (g factors g‖, g⊥ and hyperfine structure constants 161A‖, 161A⊥, 163A‖, 163A⊥) for 161Dy3+ and 161Dy3+ isotopes in the trigonal 12‐fold coordinated La3+ site of La2Mg3(NO3)12·24H2O crystal are calculated from a diagonalization (of energy matrix) method. In the method, the Zeeman and hyperfine interaction terms are added to the conventional Hamiltonian used in the studies of crystal‐field energy levels, and a 66×66 energy matrix concerning the ground multiplet 6H15/2 and the first to fifth excited multiplets 6H13/2, 6H11/2, 6H9/2, 6H7/2 and 6H5/2 are applied. The calculated results are discussed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
3.
Potassium dichromate single crystals were synthesized from aqueous solution by isothermal evaporation of the solvent. The electron paramagnetic resonance (EPR) spectra were studied from Cr5+ ions, stabilized by 60 min heating of X-irradiated crystals at 120°C. EPR spectrum was observed which consists of a strong central line and four almost equidistant satellites with intensities as weak as 2% from that of the central one. The received EPR spectrum may be described within the experimental errors by the anisotropic spin Hamiltonian, the constants at 77°K being: g∥ = 1.982 ± 0.001, g⊥ = 1.925 ± 0.001, A⊥ = 10.2 ± 0.4 G and A⊥ = 4.0 ± 0.4 G. 相似文献
4.
The spin Hamiltonian parameters (g factors g∥, g⊥ and the hyperfine structure constants A∥, A⊥) for the Cu2+ centers in the lithium potassium borate (LKB) glasses xLi2O·(30 − x)·K2O·70B2O3 (0 ≤ x ≤ 25) were theoretically studied using the high-order perturbation formulas of these parameters for a 3d9 ion in a tetragonally elongated octahedron. The [CuO6]10− clusters in the LKB glasses are found to suffer the relative elongations of about 3% along the tetragonal axis due to the Jahn-Teller effect. The concentration dependences of the g factors are illustrated by the approximately linear decrease of the cubic field parameter Dq as well as the increases of the covalency factor N and the relative elongation ratio ρ due to the slight expansion of the cell volume or bond lengths with increasing the Li2O concentration x. Meanwhile, the slow non-linear increases of the hyperfine structure constants are described as the rough exponential increase of the core polarization constant κ with x due to the increase of the tetragonality of the systems. The theoretical spin Hamiltonian parameters and their concentration dependences show good agreement with the experimental data. To evaluate validity and applicability of the present theoretical model and formulas, the EPR results of the Cu2+ centers in similar lithium sodium borate (LNB) xLi2O·(30 − x)·Na2O·70B2O3 (5 ≤ x ≤ 25 mol%) glasses are also analyzed and compared with those in the LKB systems using the uniform model and formulas. 相似文献
5.
The anisotropic g factors (gx, gy, gz) at low temperature and the motionally averaged isotropic g factor at high temperature for two Cr5+ centers, the tetragonal t‐Cr5+ center and the rhombic O‐Cr5+ center, in ferroelectric PbTiO3 are calculated from the high‐order perturbation formulas based on a two‐mechanism model. In the model, the contributions to g factors from both the crystal‐field (CF) mechanism concerning the CF excited states and the charge‐transfer (CT) mechanism (which is neglected in CF theory) concerning the CT excited states are contained. The calculated results are in reasonable agreement with the experimental values. From the calculations, the defect models of t‐Cr5+ center (which is attributed to Cr5+ in the tetragonally‐compressed octahedron caused by Jahn‐Teller effect rather than in the tetragonally‐elongated octahedron in the host PbTiO3) and O‐Cr5+ center (which is due to the t‐Cr5+ center perturbated by the electrical polarization perpendicular to the C4 axis) are confirmed, and the defect structure of t‐Cr5+ center is obtained. It is found that in the precise calculations of g factors for the high valence state d1 ions in crystals, both the contributions due to CF and CT mechanisms should be taken into account. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
A. B. Vassilikou-Dova 《Crystal Research and Technology》1991,26(1):135-138
In single crystals of scapolite from two different localities, three paramagnetic centres are detected by electron paramagnetic resonance (EPR): 1. One isotropic singlet with giso = 2.005; 2. One triclinic singlet with g‖ = 2.005 ± 0.001 and g⟂= 2.009; 3. One triclinic sextet with g‖= 2.005 ± 0.001, g⟂ = 2.011; A‖ = 85.4 × 10−4 cm−4, A⟂ = 85.3 × 10−4 cm−1. Centres 1 and 2 can be attributed to colour centres as they are bleached after annealing. Centre 3 can be due to Mn2+ (only the central Ms = ± 1/2 transition is observable) most likely substituting for Ca2+ The site symmetry must be triclinic but due to Al, Si disorder and mixed Na, Ca composition the different components from magnetically non-equivalent sites are averaged out for many orientations. 相似文献
7.
Optical absorption and EPR spectra of Li2SO4 · H2O crystals doped with Cr3+ are studied at liquid nitrogen temperature. The bands are found in absorption spectra with maxima about 17000, 23 800 and 37 200 cm−1, assigned to the 4A2 → 4T2, 4A2 → 4T1 and 4A2 → 4T1 (4P) transitions, respectively. The crystal field theory parameters were determined and appeared to be as follows: Dq = 1700 cm−1, B = 667 cm−1, C = 3002 cm−1. The lines resulting from Cr3+ ions are found in EPR spectra. All lines are doublets, which is indicative of presence of two magnetically unequivalent centre positions, and have the hyperfine structure resulting from interaction of the unpaired electron spin with Cr53 isotope nucleus. Centres are oriented in such a way, that z-axes, corresponding to two centre positions, are situated at both sides of a-axis at an angle of about 3°. Spin Hamiltonian parameters were found as follows: gx = 1.985, gy = 1.984, gz = 1.988, D = 0.130 cm−1, E = 0.016 cm−1, |A| = 17.8 · 10−4 cm−1. 相似文献
8.
Ferroelastic LuNbO4 single crystals containing 0.3 at. % Cr3+ ions have been grown by the floating zone technique, and their EPR spectra have been studied at a frequency of 9.8 GHz at room temperature. The lines on the spectra are due to the transitions caused by three paramagnetic centers formed as a result of the replacement of one isovalent position of a Lu3+ ion and two nonisovalent positions of Nb5+ions by Cr3+-ions. As a result of twinning, the line number is doubled and four principal directions arise along which the same spectra are obtained. The spectra of these centers were described by a spin Hamiltonian with S = 3/2, the D and E parameters ranging from 0.024 to 0.17 cm?1, and the g-factors g ∥ = 1.75–2.20 and g ⊥ = 1.90–2.13. 相似文献
9.
EPR spectra are studied of X-irradiated sodium dichromate crystals grown from an aqueous solution by evaporation at 31°C. Doublet lines of EPR-absorption are attributed to the Cr5+ ions in the CrO43− and CrO3− radicals resulting from radiation decomposition of Cr2O72− and being in the lattice in two unequivalent positions. Hyperfine structure caused by interaction of an unpaired electron with Cr53 nucleus were observed both at liquid nitrogen and room temperatures. For the line, caused by CrO43− radical, gy and Ay directions coincide and angles both between Ax, gx and Az, gz make up ∼ 25°. The spectrum is described by usual spin Hamiltonian for S = 1/2 with following parameters (T = 77 K): for CrO: gz = 1.984, gy = 1.970, gx = 1.961, |Az| = 8.2 · 10−4 cm−1, |Ay| = 13.7 × 10−4 cm−1, |Ax| = 36.1 · 10−4 cm−1; for CrO3−: gz = 1.915, gy = 1.975, gx = 1.985, |Az| = 32.2 · 10−4 cm−1. 相似文献
10.
C. Shiyamala T. M. Rajendiran R. Venkatesan P. Sambasiva Rao 《Crystal Research and Technology》2002,37(8):841-848
Single crystal electron paramagnetic resonance studies on VO(II) doped cadmium ammonium phosphate hexahydrate were carried out at room temperature. The paramagnetic impurity VO(II) was found to enter the host lattice both substitutionally and interstitially. The spin Hamiltonian parameter values calculated from crystal rotations for both the locations are; Site1: g∥ = 1.939, g⟂ = 1.992, A∥ = 16.3mT, A⟂ = 7.7mT and site2: g∥ = 1.933, g⟂ = 1.998, A∥ = 16.2mT, A⟂ = 7.7mT. The powder spectra values agree well with the single crystal data. The two sites have been identified as at right angles to each other. The admixture coefficients and other parameter values (κ and P) were evaluated from the spin Hamiltonian parameters. The complex was found to be fairly covalent in nature. 相似文献
11.
《Journal of Non》2006,352(32-35):3414-3422
The crystallization of fluoroindate glasses doped with Gd3+, Mn2+ and Cu2+ heat treated at different temperatures, ranging from the glass transition temperature (Tg) to the crystallization temperature (Tc), are investigated by electron paramagnetic resonance (EPR) and 19F nuclear magnetic resonance (NMR). The EPR spectra indicate that the Cu2+ ions in the glass are located in axially distorted octahedral sites. In the crystallized glass, the g-values agreed with those reported for Ba2ZnF6, which correspond to Cu2+ in a tetragonal compressed F− octahedron and to Cu2+ on interstitial sites with a square-planar F− co-ordination. The EPR spectra of the Mn2+ doped glasses exhibit a sextet structure due to the Mn2+ hyperfine interaction. These spectra suggest a highly ordered environment for the Mn2+ ions (close to octahedral symmetry) in the glass. The EPR spectra of the recrystallized sample exhibit resonances at the same position, suggesting that the Mn2+ ions are located in sites of highly symmetric crystalline field. The increase of the line intensity of the sextet and the decrease of the background line in the thermal treated samples suggest that the Mn2+ ions move to the highly ordered sites which contribute to the sextet structure. The EPR spectra of the Gd3+ doped glasses exhibit the typical U-spectrum of a s-state ion in a low symmetry site in disordered systems. The EPR of the crystallized glasses, in contrast, have shown a strong resonance in g ≈ 2.0, suggesting Gd3+ ions in environment close to cubic symmetry. The 19F NMR spin–lattice relaxation rates were also strongly influenced by the crystallization process that takes over in samples annealed above Tc. For the glass samples (doped or undoped) the 19F magnetization recoveries were found to be adjusted by an exponential function and the spin–lattice relaxation was characterized by a single relaxation time. In contrast, for the samples treated above Tc, the 19F magnetization-recovery becomes non-exponential. A remarkable feature of our results is that the changes in the Cu2+, Mn2+, Gd3+ EPR spectra and NMR relaxation, are always observed for the samples annealed above Tc. 相似文献
12.
The EPR and optical spectra of vanadium in glasses of ternary Al2O3P2O5SiO2 and Al2O3P2O5B2O3 systems have been measured. The results were compared with earlier data for vanadium in binary phosphate, aluminophosphate and silicaphosphate glasses and with results of de-Biasi for V4+ in crystalline powder α-crystobalite AlPO4. The superpositions of two hyperfine spectra (ASB-I and ASB-II) were found for many glasses of ternary systems. Both spectra can be attributed to VO2+ ions. The intensity ratio of the ASB-II spectrum to ASB-I depends on glass composition but is great (> 7) for all the glasses. Only the ASB-II spectrum was observed in glasses with low concentration of Al2O3. The spectral parameters of ASB-II spectrum are g| = 1.916–1.921; g⊥ 1.980–1.988; A| = (188?190) × 10?4cm?1 and A⊥ = (74–77) × 10?4cm?1. Three intense bands at 370, 455 and 700 ans 720 nm observed in these glasses can be attributed to V3+ ions. The excellent agreement of the parameters of the EPR spectrum of V4+ ions in crystalline α-crystobalite AIPO4 and ASB-II spectra in the glasses under study suggest the identical electron structure of the paramagnetic species. This species is believed to be characterized by optical bands at 680 and 790 nm which have been observed by de Biasi. The orbital mixing coefficients indicate strong tetragonal distortion of vanadyl complexes responsible for the ASB-II spectrum. It is assumed that VO2+ ions responsible for this spectrum act as modifiers fitting into the relatively small holes of the three-dimensional networks of phosphate glasses containing no cations of large radii. The microscopic basicity of oxygens in such holes must be about 0.48. 相似文献
13.
K. Velavan R. V. S. S. N. Ravikumar R. Venkatesan P. Sambasiva Rao 《Crystal Research and Technology》2004,39(5):448-453
The optical absorption spectra of Ni(II) doped hexaimidazole zinc(II) dichloride tetrahydrate (HZDT) and Cu(II) doped magnesium potassium phosphate hexahydrate (MPPH) have been studied at room temperature. Ni(II)/HZDT spectrum consists of three strong and one weak band. The calculated value of Dq is 1051 cm‐1 and the interelectron repulsion parameters B and C are 854 and 3626 cm‐1 respectively. The correlation of optical work with EPR has yielded the spin‐orbit interaction parameters λ and ξ as –225 and –450 cm‐1 respectively. The symmetry around the Ni(II) ion is distorted octahedral, as suggested by EPR results. The estimated percentage covalency of the nickel‐nitrogen bond is around 30%. The optical absorption studies of Cu(II)/MPPH show three bands, which are identified as 2B1g → 2A1g, 2B1g → 2B2g and 2B1g → 2Eg transitions. The octahedral field parameter Dq and the tetragonal field parameters have been evaluated from the observed adsorption bands. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
14.
Haiping Xia Hongwei Song Jinhao Wang Jiahua Zhang Tie Wang Jianli Zhang Yuepin Zhang Qiuhua Nie 《Crystal Research and Technology》2005,40(3):199-203
The growth of LiNbO3 crystals doped with Cr3+ ions in 0.1, 0.2, and 0.5 mol % concentrations by Bridgman method were reported. The Cr3+ ion concentrations in crystals were measured by inductively coupled plasma spectrometry. Electron paramagnetic resonance had been used to investigate the sites occupied by the Cr3+ ions. Two Cr3+ ion centers located at Li+ and Nb5+ sites (CrLi3+ and CrNb3+ centers, respectively) were observed. Optical absorption and temperature‐dependence emission spectra of the Cr3+ ions were reported. The crystal‐field parameters and Racah parameters of the Cr3+ ion defect sites were reported and compared with those grown by Czochralski technique. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
15.
Dinuclear iron(III) derivative of Fe2L1(OCH3)Cl2 (L1=1,3‐bis[N‐(5‐bromo‐2‐hydroxybenzylidene)‐2‐aminoethyl]‐2‐(5‐bromo‐2‐hydroxyphenyl)imidazolidine) has been synthesized, its crystal structure determined and magnetically characterized. The title compound crystallizes in orthorhombic space group Pbcn with cell parameters a = 12.9770(10), 18.7930(10), 25.2950(10) Å, V = 6168.9(6)Å3, Z = 8, Dcal = 1.951 Mg/m3. The two iron(III) ions are asymmetrically bridged by a phenoxo and methoxo groups in the compound. The iron(III) centers are separated by 3.166(3) Å. Magnetic susceptibilities of the complex were measured over the range 5 – 298 K and the observed data were successfully simulated by the equation based on the spin‐Hamiltonian operator. Magnetic susceptibility measurements indicate very weak antiferromagnetic coupling between the iron(III) ions with J = – 11.5 cm‐1. The comparison of the magnetic and structural parameters of the investigated compound is given and the nature of the magnetic super‐exchange interaction of the title compound is compared with similar dinuclear iron(III) complexes. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
16.
V. F. Shamrai A. V. Arakcheeva V. V. Grinevich A. B. Mikhailova 《Crystallography Reports》2005,50(5):779-784
The magnetic susceptibility χ(T) at 4.2 K < T < 293 K; the dependence of the magnetic moment on the magnetic field strength, M(H), at 4.2, 77, and 293 K; and the electrical resistivity ρ(T) at 4.2 K < T < 293 K are studied for samples of perovskite-phase KTaO3 obtained by both solid-phase synthesis (KTaO 3 s ) and deposition on a cathode during electrolysis of melts (KTaO 3 e ). Yellowish white KTaO 3 s powders are diamagnetic and reveal dielectric properties. Dark polycrystalline KTaO 3 e samples with metallic luster are characterized by the dependence ρ(T) typical of metals and additional paramagnetic contribution to the paramagnetic susceptibility as compared with KTaO 3 e . Changes in the properties of KTaO3 during electrocrystallization are attributed to partial reduction of tantalum. They are revealed in the structural features of KTaO 3 e (excess of tantalum as compared to the stoichiometric composition of KTaO 3 e , deficiency of the oxygen sublattice, and clearly pronounced anharmonicity of atomic vibrations). A change of the cation-anion-cation interactions, occurring owing to the overlapping of oxygen p orbitals with tantalum t2g orbitals and the formation of impurity levels near the conduction band, leads to the generation of free carriers, which make a paramagnetic contribution to the magnetic susceptibility. 相似文献
17.
G. Upender 《Journal of Non》2011,357(3):903-909
Infrared, EPR and optical absorption studies on (90-x)TeO2-10GeO2-xWO3 (7.5 ≤ x ≤ 30) glasses containing Cu2+ spin probe have been carried out. The Infrared spectral studies show that the structure of glass network consists of [TeO4], [TeO3]/[TeO3 + 1], [WO4], [WO6] and [GeO6] units in the disordered manner. Physical parameters such as density (ρ), molar volume (Vm), oxygen packing density (OPD), oxygen molar volume (Vo), optical basicity (Λ), oxide ion polarizability (αO2−), inter ionic distances and the concentration of ions per unit volume of Te, Ge, W, Cu and O have been determined. The spin-Hamiltonian parameters (g||, g⊥ and A||) of Cu2+ ions in the present glasses have been estimated from EPR spectra at 300 K. Bonding parameters such as α2, β12, β2, Γσ, and Γπ have been calculated from both optical absorption and EPR data. The observed variations in spin-Hamiltonian parameters and bonding parameters have been correlated to the structural modifications due to the WO3 incorporation into the TeO2 glass network at constant 10 mol% GeO2 content. 相似文献
18.
The EPR spectra of X-irradiated Na2Cr2O7 · 2 H2O crystals grown from the aqueous solution at room temperature are studied. Three groups of lines are detected, which marked conventionally as C1, C2 and C3. Each of the C1 and C2 line groups is a superposition of two doublets. The lines are interpreted as due to the Cr5+ ions in the distorted (stretched) oxygenous tetrahedron. The doublet structure is due to hyperfine interaction with nuclei of 1/2 spin which are protons of water. It is shown that the C1 and C2 line groups are due to the centers of the same type with different orientations in the lattice. The principal g-tensor values for these centres were as follows: gz = 1.916, gy = 1.978, gx = 1.986. 相似文献
19.
The single crystals of Methyl‐p‐Hydroxy Benzoate (MHB) were grown by solution growth technique and characterized by X‐ray diffraction (single crystal), density, melting point, UV‐Vis, FT‐IR and FT‐Raman techniques. Electron Paramagnetic Resonance (EPR) spectra of Cu2+: MHB were recorded and the spin Hamiltonian parameters were evaluated. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
20.
Raman scattering has been used to study the vibrational spectra of GaSexS1‐x layered mixed crystals at 10 K. We report the frequency dependencies of different modes on composition x, with particular emphasis on A′1(2) (A1g1) and A′1(4) (A1g2) intralayer compressional modes having low dispersion in the Brillouin zone. The appearance of additional bands is attributed to multimode behavior typically exhibited by mixed crystals of anisotropic compounds. 相似文献