共查询到20条相似文献,搜索用时 15 毫秒
1.
R.V.S.S.N Ravikumar R Komatsu A.V Chandrasekhar Y.P Reddy 《Journal of Physics and Chemistry of Solids》2003,64(2):261-264
Electron paramagnetic resonance and optical investigations of copper and chromium doped LiRbB4O7 glasses are carried out. From the results and discussions, it is predicted that both the transition metal ions exhibit octahedral environment. In the case of Cr3+, the site symmetry is near octahedral, whereas in the case of Cu2+, it is tetragonally distorted octahedral environment. Crystal field, spin-Hamiltonian and bonding parameters are evaluated. The bonding parameters are suggesting ionic. 相似文献
2.
Glasses with composition xGeO2.(0.30−x)M2O.0.70B2O3 (M=Li, K) containing 2.0 mol% of V2O5 have been prepared in the range 0.00≤x≤0.15 by normal melt quenching method. Electron paramagnetic resonance (EPR), optical transmission and absorption spectra and dc conductivity of these glasses have been studied. Spin Hamiltonian parameters (SHPs) of VO2+ ions, dipolar hyperfine coupling parameter, P, Fermi contact interaction parameter, K and molecular orbital coefficients (α2 and γ2) have been calculated. In GeO2·Li2O·B2O3 glasses there is no change in the tetragonality of the V4+O6 complex and the size of 3dxy orbit also remains unchanged with increase in GeO2 content. In GeO2·K2O·B2O3 glasses, there is an increase in the tetragonality of the V4+O6 complex and the 3dxy orbit expands with increase in GeO2 content. Values of the theoretical optical basicity, Λth, have also been reported. Optical band gap decreases with increase in GeO2 content. The dc conductivity of these glasses decreases and the activation energy increases with increase in GeO2:M2O ratio. 相似文献
3.
Cr(III)-doped Cd(HPO4)Cl·[H3N(CH2)6NH3]0.5, a new-layered cadmium phosphate, is synthesized in acidic condition at room temperature. EPR and optical studies are carried out at room temperature. Polycrystalline EPR spectrum reveals the presence of two sites of Cr(III) ions in this layered phosphate lattice with zero-field splitting values of 24.24 and 7.65 mT, indicating that Cr(III) ions are in distorted octahedral sites. The optical absorption spectrum of the sample indicates near octahedral symmetry for the dopant ions. Crystal field, inter-electronic and bonding parameters are evaluated by collaborating EPR and optical data. The evaluated parameters suggest the mode of entry of Cr(III) ion into the layered phosphate as interstitial site, and bonding between the metal and ligand is partially covalent. 相似文献
4.
A series of sodium borophosphate glasses of the composition (1−x)NaPO3−xB2O3 have been synthesised from Na2CO3, B2O3 and P2O5 and their optical and thermal properties investigated. The results show that refractive index (n) and glass transition temperature (Tg) show a maximum at about B/(B+P)=0.6 while thermal expansion coefficient (α) and thermo-optic coefficient (dn/dT) change monotonically with the B/(B+P) ratio. These observations can be interpreted based on the incorporation of BO3 and BO4 units into the glass structural network. 相似文献
5.
N.O. Gopal 《Journal of Physics and Chemistry of Solids》2004,65(11):1887-1893
Optical absorption, EPR, Infrared and Raman spectral studies have been carried out on natural clinochlore mineral. The optical absorption spectrum exhibits bands characteristic of Fe2+ and Fe3+ ions. A band observed in the NIR region is attributed to an intervalence charge transfer (Fe2+-Fe3+) band. The room temperature EPR spectrum of single crystal of clinochlore mineral reveals the dominance of Fe3+ ion exhibiting resonance signals at g=2.66; 3.68 and 4.31 besides one isotropic resonance signal at g=2.0. The EPR studies have been carried out for a polycrystalline sample in the temperature range from 103 to 443 K and for a single crystal of clinochlore mineral in the temperature range 123-297 K. The number of spins (N) participating in resonance at g=4.3 signal of the single crystal of clinochlore mineral has been calculated at different temperatures. The paramagnetic susceptibility (χ) is calculated from the EPR data at different temperatures for single crystal of clinochlore mineral. The Curie constant and Curie temperature values are evaluated from 1/χ versus T graph. The infrared spectral studies reveal the formation of Fe3+-OH complexes due to the presence of higher amount of iron in this mineral. The Raman spectrum exhibits bands characteristic of Si-O-Si stretching and Si-O bending modes. 相似文献
6.
EPR spectra of Cr3+ ions doped in potassium sodium dl-tartrate tetrahydrate single crystals are recorded at 77 K. The spin Hamiltonian and zero field parameters g, |D| and |E| are measured from the resonance lines obtained at various rotations of the magnetic field. The values obtained are: gx=1.9257±0.0002, gy=1.9720±0.0002, gz=2.0102±0.0002, |D|=313±2 (×10−4) cm−1 and |E|=101±2 (×10−4) cm−1. From the results of EPR study, the site symmetry of Cr3+ ion in the crystal is discussed. The optical absorption at room temperature is also studied. From the observed band positions, the crystal field splitting parameter (Dq) and the Racah inter-electronic repulsion parameters (B and C) are evaluated. The bonding parameters are obtained by correlating optical and EPR data and the nature of bonding in the crystal is discussed. 相似文献
7.
Glasses with composition xBi2O3·(30−x)M2O·70B2O3 (M=Li, Na) containing 2 mol% V2O5 have been prepared over the range 0≤x≤15 (x is in mol%). The electron paramagnetic resonance spectra of VO2+ of these glasses have been recorded in the X-band (≈9.3 GHz) at room temperature (RT≈300 K). Spin Hamiltonian parameters, g∥, g⊥, A∥, A⊥, dipolar hyperfine coupling parameter, P, and Fermi contact interaction parameter, K, have been calculated. The molecular orbital coefficients, α2 and γ2, have been calculated by recording the optical transmission spectra. In xBi2O3·(30−x)Li2O·70B2O3 glasses there is decrease in the tetragonality of the V4+O6 complex for x up to 6 mol% whereas for x≥6 mol%, tetragonality increases. In xBi2O3·(30−x)Na2O·70B2O3 glasses there is increase in the tetragonality of the V4+O6 complex with increasing x. The 3dxy orbit expands with increase in Bi2O3:M2O ratio. Values of the theoretical optical basicity, Λth, have also been reported. The DC conductivity increases with increase in temperature. The order of conductivity is 10−5 ohm−1 m−1 at low temperature and 10−3 ohm−1 m−1 at high temperature. The DC conductivity decreases and the activation energy increases with increase in Bi2O3:M2O ratio. 相似文献
8.
The paramagnetic center of tetragonal symmetry formed by the Yb3+ ion in the KZnF3 crystal has been studied using methods of EPR, ENDOR and optical spectroscopy. The location of the impurity ion and the structural model of the complex differing from the model of the Yb3+ center in KMgF3 have been established. The empirical scheme of the energy levels of the Yb3+ ion has been found. The parameters of its interaction with the crystal electrostatic field and the hyperfine interaction with ligands of the nearest environment have been determined. The parameters of the crystal field were used for the analysis of the distortions of the crystal lattice in the vicinity of Yb3+. The parameters of the transferred hyperfine interaction have been calculated for the distances between Yb3+ and F− ions of the nearest environment obtained taking into account the found distortions. They are in good agreement with the experimental values. 相似文献
9.
B. Deva Prasad Raju K.V. Narasimhulu J. Lakshmana Rao 《Journal of Physics and Chemistry of Solids》2005,66(5):753-761
X-band electron paramagnetic resonance (EPR) studies on divalent copper ions embedded in KMgClSO4·3H2O single crystals have been performed at low temperature (123 K). The angular variation of the EPR spectra reveals the presence of two Cu2+ sites, which have different orientations. The spin-Hamiltonian parameters of this six-coordinated cupric ion have been evaluated from the EPR spectra at 123 K. The forbidden lines due to ΔmI=±1 transitions are observed in between allowed transitions. The temperature variation EPR studies have also been performed both for a single crystal and a polycrystalline sample. The ground state wavefunction of Cu2+ ions has been estimated and is found to be an admixture of d3z2−r2 and dx2−y2. The temperature variation of the EPR spectra reveals that Cu2+ ions exhibit dynamic Jahn-Teller effect. From the polycrystalline EPR data, the temperature dependent magnetic susceptibilities are evaluated and discussed. 相似文献
10.
Electron paramagnetic resonance (EPR) spectra of Cu2+ ion in ammonium dihydrogen phosphate are studied at liquid nitrogen temperature (77 K). Four magnetically inequivalent Cu2+ sites in the lattice are identified. The angular variation spectra of the crystal in the three orthogonal planes indicate that the paramagnetic impurity, Cu2+ enters the lattice substitutionally in place of NH4+ ions. The spin Hamiltonian parameters are determined with the fitting of spectra to rhombic symmetry crystalline field. The ground state wave function of Cu2+ ion is constructed and found to be predominantly |x2-y2〉. The cubic field parameter (Dq) and tetragonal parameters (Ds and Dt) are determined from optical spectra at room temperature. By correlating EPR and optical absorption spectra, the bonding coefficients are calculated and nature of bonding of metal ion with different ligands in the crystal is discussed. 相似文献
11.
S. Boobalan 《Journal of Physics and Chemistry of Solids》2010,71(11):1527-1533
In order to understand the structural behaviour of Cu(II) in a variety of ligand environments, single crystal electron paramagnetic resonance studies of Cu(II) doped in hexaaquazincdiaquabis(malonato)zincate [Zn(H2O)6][Zn(mal)2(H2O)2] are carried out at 300 K. Angular variation of copper hyperfine lines in three orthogonal planes shows the presence of single site, with spin Hamiltonian parameters as gxx=2.034, gyy=2.159, gzz=2.388, Axx=3.39 mT, Ayy=4.89 mT and Azz=13.72 mT. The g/A tensor direction cosines are compared with various Zn-O directions in the host lattice, which confirm that Cu(II) enters substitutionally in the lattice. The low value of Azz has been explained by considering admixture of d2x−2y ground state with d2z excited state. EPR powder spectra at 300 and 77 K give identical spin Hamiltonian parameters (g∥=2.367, g⊥=2.088, A∥=11.47 mT, A⊥=2.63 mT). IR, UV-vis and powder XRD data confirm the structure and symmetry of the Cu(II) ion in the host lattice. 相似文献
12.
W.L. Feng L.C. PuX.Z. Yang N. Hu 《Journal of magnetism and magnetic materials》2011,323(22):2828-2830
In this paper, the nickel site, optical spectra and electron paramagnetic resonance (EPR) g factor of nickel-zinc phosphate glasses have been studied by ligand-field theory. The orbital mixing effect between p and d orbits has been included in the calculation by two-spin-orbit parameter model. The present study shows that nickel occupies the tetrahedral zinc site with cubic symmetry in nickel-zinc phosphate glasses. Unlike the result of previous study that assigns nickel to an octahedral interstitial site, it is an optional explanation for nickel sites in nickel-zinc phosphate glasses by analysing the optical absorption spectra and EPR g factor. 相似文献
13.
Huang Jin-Ling Kuang Xiao-Yu Mao Ai-Jie Wang Hui 《Journal of Physics and Chemistry of Solids》2008,69(4):913-917
The local lattice structure distortions for YAG and YGG systems doped with Cr3+ have been investigated by the d3 configuration complete energy matrices which contain the Zeeman energy besides the electron–electron interaction, the trigonal crystal field as well as the spin–orbit coupling interaction. The local lattice structure parameters R and θ of (CrO6)9− complex are determined for Cr3+ in YAG and YGG systems, respectively. The calculated results show that the local lattice structures have expansion distortions, which almost tend to the same after distortions. Meanwhile, the EPR parameter D, g factors (g||, g) and optical spectrum of these systems have been interpreted uniformly by quantitative calculation. It is shown that the effect of the orbit reduction factor k on g factors (g||, g) cannot be ignored. 相似文献
14.
Cheng-Gang Li Mei-Ling Duan Ya-Ru Zhao 《Journal of Physics and Chemistry of Solids》2010,71(11):1599-1602
The local lattice structure and EPR parameters (D, g‖, g⊥) have been studied systematically on the basis of the complete energy matrix for a d3 configuration ion in a trigonal ligand field. By simulating the calculated optical and EPR spectra data to the experimental results, the local distortion parameters (ΔR, Δθ) are determined for V2+ ions in CdCl2 and CsMgCl3 crystals, respectively. The results show that the local lattice structure of CdCl2:V2+ system exhibits a compression distortion (ΔR=−0.0868 Å) while that of CsMgCl3:V2+ system exists an elongation distortion (ΔR=0.0165 Å). The different distortion may be ascribed to the fact that the radius of V2+ ion is smaller than that of Cd2+ ion or larger than that of Mg2+ ion. Moreover, the relationships between EPR parameter D and local structure parameters (R, θ) as well as the orbital reduction factor k and g‐factors (g‖, g⊥) are discussed. 相似文献
15.
D.V. Azamat A. Dejneka J. Lančok L. Jastrabik V.A. Trepakov Z. Bryknar E.V. Neverova A.G. Badalyan 《Journal of Physics and Chemistry of Solids》2014
The trivalent chromium centers were investigated by means of electron paramagnetic resonance (EPR) in SrTiO3 single crystals grown using the Verneuil technique. It was shown that the charge compensation of the Cr3+-VO dominant centers in octahedral environment is due to the remote oxygen vacancy located on the axial axis of the center. In order to provide insight into spin-phonon relaxation processes the studies of axial distortion of Cr3+-VO centers have been performed as function of temperature. The analysis of the trigonal Cr3+ centers found in SrTiO3 indicates the presence of the nearest-neighbor strontium vacancy. The next-nearest-neighbor exchange-coupled pairs of Cr3+ in SrTiO3 has been analyzed from the angular variation of the total electron spin of S=2 resonance lines. 相似文献
16.
V. Ramesh Kumar N.O. Gopal R.P.S. Chakradhar 《Journal of Physics and Chemistry of Solids》2004,65(7):1367-1372
Electron paramagnetic resonance (EPR), luminescence and infrared spectra of Mn2+ ions doped in zinc gallate (ZnGa2O4) powder phosphor have been studied. The EPR spectra have been recorded for zinc gallate phosphor doped with different concentrations of Mn2+ ions. The EPR spectra exhibit characteristic spectrum of Mn2+ ions (S=I=5/2) with a sextet hyperfine pattern, centered at geff=2.00. At higher concentrations of Mn2+ ions, the intensity of the resonance signals decreases. The number of spins participating in the resonance has been measured as a function of temperature and the activation energy (Ea) is calculated. The EPR spectra of ZnGa2O4: Mn2+ have been recorded at various temperatures. From the EPR data, the paramagnetic susceptibility (χ) at various temperatures, the Curie constant (C) and the Curie temperature (θ) have been evaluated. The emission spectrum of ZnGa2O4: Mn2+ (0.08 mol%) exhibits two bands centered at 468 and 502 nm. The band observed at 502 nm is attributed to 4T1→6A1 transition of Mn2+ ions. The band observed at 468 nm is attributed to the trap-state transitions. The excitation spectrum exhibits two bands centered at 228 and 280 nm. The strong band at 228 nm is attributed to host-lattice absorption and the weak band at 280 nm is attributed to the charge-transfer absorption or d5→d4s transition band. The observed bands in the FT-IR spectrum are assigned to the stretching vibrations of M-O groups at octahedral and tetrahedral sites. 相似文献
17.
R.C. Santana M.G. Santos K.D. Ferreira R. Calvo 《Journal of Physics and Chemistry of Solids》2006,67(4):745-750
We report an electron paramagnetic resonance (EPR) study at 33.9 GHz and room temperature of oriented single crystal samples of bis(l-asparaginato)Zn(II) doped with Cu(II). The variation of the spectra with magnetic field orientation was measured in three crystal planes (a*b, bc and a*c, with a*=b×c). These spectra display two groups of four peaks arising from the hyperfine interaction with the ICu=3/2 nuclear spins of copper. They were assigned to Cu(II) ions in two lattice sites related by a 180° rotation around the b-crystal axis. The g and hyperfine coupling (A) tensors of the Cu(II) ions were evaluated from the single crystal data. Some indeterminacy in the assignment of the signals was avoided measuring the EPR spectrum of a powder sample. Their principal values are g1=2.060(1), g2=2.068(2), g3=2.283(2), and A1≈0.1×10−4, A2=13×10−4 and A3=165×10−4 cm−1. The eigenvectors corresponding to g3 and A3 are coincident within the experimental error; the other eigenvectors are rotated 5.6° in the perpendicular plane. Considering the crystal structure of bis(l-asparaginato)Zn(II), our EPR results indicate that the Cu(II) impurities replace Zn(II) ions in the host crystal. We propose a molecular model based on the EPR data and the structural information, and analyse the results comparing the measured values with those obtained in similar systems. 相似文献
18.
19.
Masahiro Takesada 《Journal of Physics and Chemistry of Solids》2009,70(2):281-6320
We characterized ZnGa2O4:Mn2+ (ZnGa2O4—zinc gallate) nanophosphor synthesized by the solvothermal method in 1,4-butanediol-containing water to increase the amount of Mn2+ ions incorporated in the ZnGa2O4 matrix without post-heat treatment. We investigated the influence of water content in the solvent on the photoluminescence (PL) intensity and the Mn amount, the latter being measured by X-ray fluorescence analysis and electron paramagnetic resonance spectroscopy. The PL intensity per Mn amount reached the maximum at the 50 wt% water content. The addition of water promotes repeated dissolution and precipitation, resulting in homogeneous Mn2+ distribution in the ZnGa2O4 matrix. This suggests that the solvothermal method in the 1,4-butanediol-water system is useful for increasing the amount of Mn2+ ions incorporated in the ZnGa2O4 matrix without post-heat treatment. At the water content >50 wt%, the decrease in PL intensity is attributed to the optical absorption of the by-product, MnOOH. 相似文献
20.
The dependence of the EPR g-factors on the local structural parameter for a 4f11 configuration ion Er3+ in a trigonal crystal-field has been studied by diagonalizing the 364×364 complete energy matrices. Our studies indicate that the EPR spectra of the trigonal Er3+–VK centers in KMgF3 and KZnF3 may be attributed to the translation of the cubic Kramers doublet Γ7. Furthermore, the EPR g-factors of the trigonal Er3+–VK centers may be interpreted reasonably by the shifts ΔZ≈0.340 Å and ΔZ≈0.303 Å of the Er3+ ions toward the charge compensator VK along the C3 axis for the KMgF3:Er3+ and the KZnF3:Er3+ systems respectively. 相似文献