On the basis of the crystal field theory, the formulae of the EPR g factors of three order perturbation with b 2g ground state for 3d 9/3d 1 ions at rhombic tetrahedral clusters (AX 4) n- have been obtain...On the basis of the crystal field theory, the formulae of the EPR g factors of three order perturbation with b 2g ground state for 3d 9/3d 1 ions at rhombic tetrahedral clusters (AX 4) n- have been obtained. Using these formulae, The authors investigated the EPR g factors of the crystals Cs 2CuCl 4 and T 2CuBr 4. The calculation results agree with the experimental findings.展开更多
We report combined magnetic susceptibility, dielectric constant, nuclear quadruple resonance （NQR）, and zero-field nuclear magnetic resonance （NMR） measurements on single crystals of multiferroics CuBr2. High qual...We report combined magnetic susceptibility, dielectric constant, nuclear quadruple resonance （NQR）, and zero-field nuclear magnetic resonance （NMR） measurements on single crystals of multiferroics CuBr2. High quality of the sample is demonstrated by the sharp magnetic and magnetic-driven ferroelectric transition at TN = TC≈74 K. The zero-field 79Br and 81Br NMR are resolved below TN. The spin-lattice relaxation rates reveal charge fluctuations when cooled below 60 K. Evidences of an increase of NMR linewidth, a reduction of dielectric constant, and an increase of magnetic susceptibility are also seen at low temperatures. These data suggest an emergent instability which competes with the spiral magnetic ordering and the ferroelectricity. Candidate mechanisms are discussed based on the quasi-one-dimensional nature of the magnetic system.展开更多
Copper ion is the essential microelement to many organisms. In this paper, the local structure of Cu2+ in CuBr2 aqueous solutions with different concentrations are investigated by using X-ray absorption fine structure...Copper ion is the essential microelement to many organisms. In this paper, the local structure of Cu2+ in CuBr2 aqueous solutions with different concentrations are investigated by using X-ray absorption fine structure (XAFS) technique. XANES (X-ray Absorption Near Edge Structure) spectra indicate that charge transfer from Br- to Cu2+ decreases with the solution concentration, which lead to a shift of the absorption edge. The shoulder appearing at the rising edge proves to be characteristic of a tetragonal distortion. The Fourier transform magnitudes of EXAFS (Extended X-ray absorption fine structure) data of Cu species suggest that more Cu-Br bonds may exist in high concentrations. A fivefold coordination configuration like a pyramid is used as the fitting parameters. From the analysis of the coordination numbers, the proportion of Cu-O and Cu-Br is 4:1 in the saturated solution. The Br atom is on the equatorial plane of the model. The fitting results agree well with the experiment data.展开更多
文摘On the basis of the crystal field theory, the formulae of the EPR g factors of three order perturbation with b 2g ground state for 3d 9/3d 1 ions at rhombic tetrahedral clusters (AX 4) n- have been obtained. Using these formulae, The authors investigated the EPR g factors of the crystals Cs 2CuCl 4 and T 2CuBr 4. The calculation results agree with the experimental findings.
基金Project supported by the Ministry of Science and Technology of China(Grant No.2016YFA0300504)the National Natural Science Foundation of China(Grant No.11374364)+1 种基金the Fundamental Research Funds for the Central Universities of Chinathe Research Funds of Renmin University,China(Grant No.14XNLF08)
文摘We report combined magnetic susceptibility, dielectric constant, nuclear quadruple resonance （NQR）, and zero-field nuclear magnetic resonance （NMR） measurements on single crystals of multiferroics CuBr2. High quality of the sample is demonstrated by the sharp magnetic and magnetic-driven ferroelectric transition at TN = TC≈74 K. The zero-field 79Br and 81Br NMR are resolved below TN. The spin-lattice relaxation rates reveal charge fluctuations when cooled below 60 K. Evidences of an increase of NMR linewidth, a reduction of dielectric constant, and an increase of magnetic susceptibility are also seen at low temperatures. These data suggest an emergent instability which competes with the spiral magnetic ordering and the ferroelectricity. Candidate mechanisms are discussed based on the quasi-one-dimensional nature of the magnetic system.
基金Supported by National Natural Science Foundation of China (Grant No.11005148,10705046,11135008)National Basic Research Program of China (Grant No. 2010CB934501)+1 种基金Special Presidential Foundation of the Chinese Academy of Science (Grant No. 29)Science and Technology Commission of Shanghai Municipality (Grant No. 11JC1414900)
文摘Copper ion is the essential microelement to many organisms. In this paper, the local structure of Cu2+ in CuBr2 aqueous solutions with different concentrations are investigated by using X-ray absorption fine structure (XAFS) technique. XANES (X-ray Absorption Near Edge Structure) spectra indicate that charge transfer from Br- to Cu2+ decreases with the solution concentration, which lead to a shift of the absorption edge. The shoulder appearing at the rising edge proves to be characteristic of a tetragonal distortion. The Fourier transform magnitudes of EXAFS (Extended X-ray absorption fine structure) data of Cu species suggest that more Cu-Br bonds may exist in high concentrations. A fivefold coordination configuration like a pyramid is used as the fitting parameters. From the analysis of the coordination numbers, the proportion of Cu-O and Cu-Br is 4:1 in the saturated solution. The Br atom is on the equatorial plane of the model. The fitting results agree well with the experiment data.
