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1.
X-band single-crystal electron paramagnetic resonance (EPR) studies are done on VO2+ ions doped in potassium hexaaquazinc (II) sulfate, K2[Zn (H2O)6] (SO4)2 (PHZS) at room temperature. The spin Hamiltonian parameters, i.e., g and A tensors and their direction cosines, are evaluated by the standard diagonalization procedure using angular variation of the EPR spectra in three planes (ab, bc* and c*a), with the help of a computer program. The EPR spectrum is simulated using the EasySpin program to verify the calculations. The detailed EPR analysis indicates the presence of two magnetically inequivalent VO2+ sites. Both the vanadyl complexes are found to take up the substitutional position in the host lattice. The optical absorption spectrum of VO2+ ions doped in PHZS single crystal at room temperature is also recorded and four main dd transfer bands in the visible region are assigned. The theoretical band positions are obtained using energy expressions and a good agreement is found with the experimental values. With the help of assigned bands the crystal-field parameters (Dq, Ds and Dt) are evaluated. Finally, with the optical and EPR data, the nature of bonding in the complex is discussed.  相似文献   

2.
A Cu2+-doped single crystal of catena-trans-bis(N-(2-hydroxyethyl)-ethylenediamine) zinc(II)-tetra-m-cyanopaladate(II) [ZnPd(CN)4(C4H12N2O2)] complex has been investigated by electron paramagnetic resonance (EPR) technique at room temperature. EPR spectra indicate that Cu2+ ions substitute for magnetically equivalent Zn2+ ions and form octahedral complexes in [ZnPd(CN)4(C4H12N2O2)] hosts. The crystal field affecting the Cu2+ ion is nearly axial. The optical absorption studies show two bands at 322 nm (30864 cm−1) and 634 nm (15337 cm−1) which confirm the axial symmetry. The spin Hamiltonian parameters and the relevant wave function are determined.  相似文献   

3.
Cu2+-doped ZnO nanopowders, synthesized at room temperature by mild and simple solution method, are characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), optical, electron paramagnetic resonance (EPR) and Fourier-transform infrared (FT-IR) techniques. From XRD and SEM, the crystal structure is identified as hexagonal, and the average crystallite size is around 53 nm. Lattice cell parameters are evaluated. The optical and EPR spectral investigations suggest that the Cu2+ ion enters the host lattice in two tetragonally distorted octahedral sites. Crystal field, tetragonal field, spin Hamiltonian and bonding parameters are estimated.  相似文献   

4.
The Cr3+-doped cadmium oxide nanopowder is prepared at room temperature by a mild and simple solution method. The prepared powder is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical, electron paramagnetic resonance (EPR) and Fourier transform infrared (FT-IR) techniques. The XRD powder pattern reveals the lattice structure and cell parameters are evaluated. The SEM image shows the stone-like morphology of the nanopowder. The optical absorption spectrum indicates the distorted octahedral site symmetry of Cr3+ ions. The crystal field Dq and interelectronic repulsion parameters B and C are evaluated. The EPR spectrum gives a resonance signal at g = 1.973 for Cr3+ ions. The FT-IR spectrum reveals the characteristic vibrations of cadmium oxide.  相似文献   

5.
Electron paramagnetic resonance (EPR) study of Cu2+-doped sodium zinc sulfate tetrahydrate is done at liquid nitrogen temperature. Two magnetically equivalent sites for Cu2+ are observed. The spin-Hamiltonian parameters determined by fitting the EPR spectra to the rhombic-symmetry crystalline field are g x  = 2.2356, g y  = 2.0267, g z  = 2.3472, A x  = 27 × 10−4 cm−1, A y  = 54 × 10−4 cm−1and A z  = 88 × 10−4 cm−1. The ground state wave function is also determined. The g-anisotropy is evaluated and compared with the experimental value. With the help of optical study, the nature of bonding in the complex is discussed.  相似文献   

6.
The electron paramagnetic resonance (EPR) parameters (g-factors g , g and zero-field splitting D) of two tetragonal 3d3 impurity centers M3d-VMg and M3d-Li+ (where M3d = Cr3+ or Mn4+, VMg is the Mg2+ vacancy) in M3d-doped MgO crystals are calculated from the high-order perturbation formulas including both the crystal-field (CF) and the charge-transfer (CT) mechanisms for 3d3 ions in the tetragonal symmetry. The calculated results are in reasonable agreement with the experimental values. From the calculations, it can be found that the relative importance of the CT mechanism for EPR parameters increases with increasing valence state of the 3d3 ion. So, for the high-valence 3d n ions in crystals, a reasonable explanation of EPR parameters should take into account both CF and CT mechanisms. The defect structures (characterized by the displacement ΔR of O2− in the intervening M3d and VMg or Li+ at the Mg2+ site) for these tetragonal impurity centers are obtained from the calculations. The results are consistent with the expectations based on the electrostatic interactions.  相似文献   

7.
Physical and spectral studies on 20ZnO + xLi2O + (30-x)Na2O + 50B2O3 (5 ≤ x ≥ 25) doped with 0.1 mol% of paramagnetic CuO impurity are carried out. Powder X-ray diffraction patterns of the glass samples confirm the amorphous nature. The physical parameters of all the glasses were also evaluated with respect to the composition. The electron paramagnetic resonance spectra of all these glasses exhibit resonance signals that are characteristic of Cu2+ ions. The optical absorption spectra also confirm the Cu2+ ion in tetragonally elongated octahedral site. Various crystal field, spin-Hamiltonian and bonding parameters are evaluated. It is observed that the mixed alkali effect is significant.  相似文献   

8.
The electron paramagnetic resonance (EPR) parameters (g andg factors and hyperfine structure constantsA ,A ) for Co2+ in Ca(OH)2 are studied from the second-order perturbation formulas on the basis of the cluster approach. In these formulas, the contributions to EPR parameters from the state interactions and covalency effects are considered and the parameters related to both effects are obtained from the optical spectra and impurity structure of the studied system. From the study, it is found that the β angle between the metal-ligand bond and the C3 axis changes from 61° in a pure crystal to 53.68(26)° in the impurity center of a Co2+-doped Ca(OH)2 crystal because of the impurity-induced local lattice relaxation. The reduction of the angle β in the impurity center is also supported by the result obtained by analyzing the EPR zero-field splitting for Mn2+ in the same Ca(OH)2 crystal. The EPR parameters of Ca(OH)2:Co2+ are also reasonably explained by considering the suitable local lattice relaxation.  相似文献   

9.
Electron paramagnetic resonance (EPR) and optical absorption studies of Li2O–MoO3–B2O3 with varying concentrations of Li2O, MoO3 and B2O3 have been carried out at room temperature. Two series of glasses, one with constant MoO3 (CM) and another with constant borate (CB), have been investigated. Characteristic EPR spectra of Mo5+ have been observed centered around g ≅ 2.00, which are attributed to Mo5+ ion in an octahedral coordination sphere with an axial distortion. The spectra also show strong dependence on the concentration of Li2O and B2O3. Spin concentrations (N) and magnetic susceptibilities (χ) have been calculated. In the CM series, the N values decrease with increasing Li2O content up to 30 mol%, while in the CB series variation of N is found to increase initially up to 20 mol%, and with further increase in the Li2O content the N values tend to decrease. The variation of magnetic susceptibilities is almost similar to that observed with the variation of N. From the optical absorption spectra, an absorption edge (α) has been evaluated. In the CM series, the values of α show a blueshift. On the other hand, in the CB series a redshift is observed. The observed variations in spectral parameters are explained by considering the molybdoborate network. Addition of Li2O to the CM and CB series results in modification of [MoO6/2]0 → [MoOO5/2] and [BO3/2]0 → [BO4/2] → [BOO2/2] groups, respectively, leading to creation of nonbridging oxygens. The optical basicity of the glasses has been evaluated in both the CM and the CB glasses. The optical basicity can be used to classify the covalent-to-ionic ratios of the glass, since an increasing optical basicity indicates decreasing covalency. It is observed that the covalency between Mo5+ ions and oxygen ligands increases in the CB series, whereas in the CM series the covalency between Mo5+ ions and oxygen ligands decreases. Authors' address: R. P. Sreekanth Chakradhar, Glass Technology Laboratory, Central Glass and Ceramic Research Institute, Kolkata 700032, India  相似文献   

10.
The electron paramagnetic resonance study of Cu2+-doped bis(l-asparaginato)Mg(II) is performed at room temperature. Two magnetically non-equivalent sites for Cu2+ are observed. The spin-Hamiltonian parameters evaluated by fitting spectra to the crystalline field of rhombic symmetry are as follows: g x  = 2.0420 ± 0.0002, g y  = 2.0808 ± 0.0002, g z  = 2.3600 ± 0.0002, A x  = (99 ± 2) × 10−4 cm−1, A y  = (108 ± 2) × 10−4 cm−1, A z  = (140 ± 2) × 10−4 cm−1. The ground state wave function of Cu2+ is also determined. The g-anisotropy is estimated and compared with the experimental value. Further, with the help of optical study the nature of bonding of a metal ion with different ligands in the complex is discussed.  相似文献   

11.
Electron paramagnetic resonance of Cu2+-doped catena-trans-bis(N-(2-hydroxyethyl)-ethylenediamine) zinc(II)-tetra-μ-cyanonicelate(II) [Zn(NH2(CH2)3NHOH)2Ni(CN)4] single crystals and powder are examined at room temperature. The spectra show the substitution of the Zn2+ ion with the Cu2+ ion. The crystal field around the Cu2+ ion is nearly axial. There is a single paramagnetic site withg xx=2.073,g yy=2.060,g zz=2.248,A xx=40.5 G,A yy=50.8 G,A zz=172.0 G. The ground-state wave function is an admixture of d x 2y 2 and d z 2 states. The optical-absorption studies show two bands at 320 nm (31250 cm−1) and 614 nm (16286 cm−1) which confirm the axial symmetry. The crystal field parameters and the wave function are determined.  相似文献   

12.
The natural forsterites and their synthetic analogs were investigated on a wide-band EPR spectrometer in the frequency region of 65–850 GHz. Two types of non-Kramers ions Fe2+ were discovered at the site M1 (inversion symmetry) and M2 (mirror plane symmetry). The ratio of concentrations of Fe2+ in these positions was measured in synthetic and natural crystals. The features of EPR spectra of synthetic and natural forsterite are discussed. Spin Hamiltonian with S = 1 was used for theoretical treatment of angular and field–frequency dependences.  相似文献   

13.
The electron paramagnetic resonance (EPR) spectra of Ce3+ and Nd3+ impurity ions in unoriented powders of the YBa2Cu3O6.13 compound are observed and interpreted for the first time. It is demonstrated that, upon long-term storage of the samples at room temperature, the EPR signals of these ions are masked by the spectral line (with the g factor of approximately 2) associated with the intrinsic magnetic centers due to the significant increase in its intensity.  相似文献   

14.
We have synthesized Dy3+-doped ZnO nanoparticles at room temperature through the sol–gel method. X-ray diffraction and Scanning electron microscopic studies confirm the crystalline nature of the particles. Excitonic absorption of ZnO shows three different bands, and we observe that incorporation of Dy3+ results in the shifting and broadening of the n=1 absorption band of ZnO. Photoluminescence studies done at the excitation wavelength of 335 nm show broad emission containing five different bands. Open-aperture z-scan studies done at 532 nm using 5 ns laser pulses show an optical limiting behavior, which numerically fits to a three-photon type absorption process. The nonlinearity is essentially resonant, as it is found to increase consistently with Dy3+ concentration. This feature makes Dy3+-doped ZnO a flexible optical limiter for potential device applications.  相似文献   

15.
In this report, we described the preparation of Cu2+/nitrilotriacetic acids (NTA)-derivatized branch polyglycerol magnetic nanoparticles for protein adsorption with avoidance of nonspecific interactions at the same time. Magnetic nanoparticles (MNPs) were synthesized by the coprecipitation method. The transmission electron microscopy results showed that the average diameter of MNPs was 15.8 ± 4.6 nm. X-ray photoelectron spectroscopy and Fourier Transform infrared measurements indicated that branch polyglycerols were grafted on MNPs via the ring-opening polymerization of glycidol and that Cu2+ ions had been successfully immobilized on the surface of MNPs. The protein immobilization effect was characterized by UV–Vis spectrum. The results proved that Cu2+/NTA-derivatized branch polyglycerol magnetic nanoparticles effectively adsorbed bovine haemoglobin and rarely adsorbed lysozyme and γ-globin.  相似文献   

16.
Electron Paramagnetic Resonance (EPR) and optical absorption spectra of Cu2+ ions in sodium–lead borophosphate glasses doped with different concentrations of Cu2+ ions have been studied. EPR spectra of all the glass samples exhibit resonance signals characteristic of Cu2+ ions. The values of spin-Hamiltonian parameters indicate that the Cu2+ ions in sodium–lead borophosphate glasses are present in octahedral sites with tetragonal distortion. The optical absorption spectra of all the glass samples show a single broad band, which has been assigned to the 2B1g2B2g transition of Cu2+ ions. The optical band gap energy (Eopt) and Urbach energy (ΔE) are calculated from their ultraviolet absorption edges. The emission bands observed in the ultraviolet and blue region are attributed to 3d94s→3d10 triplet transition in Cu+ ion. The FT-IR spectra show that the glass system contains BO3, BO4 and PO4 structural units.  相似文献   

17.
The projection of integrating optical, magnetic and electronic functionalities into a single material have aggravated passionate attention in mounting wide band gap diluted magnetic semiconductor (DMS) in the midst of room temperature ferromagnetism. We report the evidence of ferromagnetism in Cu-doped ZnSe quantum dots (QDs) below room temperature, grown from a single source precursor by lyothermal method with the sizes of approximately 3.2–5.14 nm. QDs mainly exhibit paramagnetic behavior between 80 and 300 K, with a weak ferromagnetic/anti-ferromagnetic exchange at lower temperature as observed by superconducting quantum interference device (SQUID) magnetometer. From the Curie–Weiss behavior of the susceptibility, Curie temperature (T c) of Cu-doped ZnSe sample has been evaluated. From EPR, we obtain the Lande-g factor in the Zeeman interaction term as 2.060. Photoluminescence and EPR measurements support and confirm the view that Cu2+ substitutes for Zn2+ in Cu-doped ZnSe quantum dots.  相似文献   

18.
Single crystals of gadolinium orthosilicate Gd2SiO5 containing 0.5 at% and 5 at% of Sm3+ were grown by the Czochralski method. Optical absorption spectra, luminescence spectra and luminescence decay curves were recorded for these systems at 10 K and at room temperature. Comparison of optical spectra recorded in polarized light revealed that the anisotropy of this optically biaxial host affects the intensity distribution within absorption and emission bands related to transitions between multiplets rather than the overall band intensity. It has been found that among four bands of luminescence related to the 4G5/26HJ (J=5/2–11/2) transitions of Sm3+ in the visible and near infrared region the 4G5/26H7/2 one has the highest intensity with a peak emission cross section of 3.54×10−21 cm2 at 601 nm for light polarized parallel to the crystallographic axis c of the crystal. The luminescence decay curve recorded for Gd2SiO5:0.5 at% Sm3+ follows a single exponential time dependence with a lifetime 1.74 ms, in good agreement with the 4G5/2 radiative lifetime τ rad=1.78 ms calculated in the framework of Judd-Ofelt theory. Considerably faster and non-exponential luminescence decay recorded for Gd2SiO5:5 at% Sm3+ sample was fitted to that predicted by the Inokuti-Hirayama theory yielding the microparameter of Sm3+–Sm3+ energy transfer C da=1.264×10−52 cm6×s−1.  相似文献   

19.
EPR spectra of VO2+ ions doped in KZnClSO4·3H2O single crystals have been studied at different temperatures. The EPR spectrum shows a well-resolved hyperfine and superhyperfine structure patterns. The angular variation of EPR spectra reveals the presence of more than three magnetic complexes, which correspond to distinct sites of VO2+ ion. From the angular variation EPR data, the spin-Hamiltonian parameters are evaluated and discussed. The optical absorption spectrum studied at room temperature shows bands corresponding to C4v symmetry. From the EPR and optical data, the molecular-orbital bonding coefficient ε2 and β2 are evaluated and discussed. The observed five-line superhyperfine structure has been attributed to four protons (with I=1/2) from the surrounding water molecules of one of the vanadyl sites.  相似文献   

20.
Electron paramagnetic resonance (EPR) spectra of doped paramagnetic crystals LiLuF4:U3+ and LiYF4:Yb3+ have been investigated at a frequency of about 9.42 GHz in the temperature range of 10–20 K. The U3+ ion spectrum is characterized by g-factors g = 1.228 and g = 2.516, and contains the hyperfine structure due to the 235U isotope with nuclear spin I = 7/2 and natural abundance of 0.71%. The observed hyperfine interaction constants are A = 81 G and A = 83.8 G. Moreover, the spectrum reveals the well-resolved superhyperfine structure (SHFS) due to two groups of four fluorine ions forming the nearest surrounding of the U3+ ion. This SHFS contains up to nine components with the spacing between components being about 12.7 G. The SHFS is observed also in the EPR spectrum of the LiYF4:Yb3+ crystal; up to 17 components with spacing of about 3.7 G may be traced. Some parameters of the effective Hamiltonian of the SHF interaction are estimated, the contribution of covalent bonding of f-electrons with ligands into these parameters is discussed. Authors' address: Igor N. Kurkin, Kazan State University, Kremlevskaya ulitsa 18, Kazan 420008, Russian Federation  相似文献   

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