Electron Spin Resonance In CuCrS2 and CuCrSe2 Single Crystals

Abstract

Single crystal ESR spectra of CuCrS₂ and CuCrSe₂ have been measured at both X- and Q-band frequencies. Anisotropic signals from the localised Cr³⁺ d-electrons give zero-field splitting parameters of 0.29cm^?1 and 0.31cm^?1 for the sulphide and selenide respectively, suggesting a possible orbital interaction between the Cr and Cu ions. The dependence of the ESR parameters on temperature shows the effect of magnetic ordering.     

Electron Spin Resonance of Highly Anisotroic Organic Systems

After a brief discussion concerning the chemical nature and structural organization, ESR results obtained on low and highly conducting quasi one-dimensional organic systems, are presented. Related to the knowledge of the molecular properties, invaluable informations about the properties of the linear chains may be obtained on single crystals from the susceptibility, the g tensor and the line shape: existence of magnetically inequivalent sites, respective contributions of the different magnetic species (for low conducting systems) or of the different chains (for highly conducting systems). In particular cases, the existence of weak intrachain coupling has been pointed out and even some order of magnitude for the ratio of intra- to interchain exchange have been reached.     

酸处理对碳纳米管电子自旋共振谱的研究

采用浓硫酸与硝酸混酸对碳纳米管的进行了酸氧化处理,并采用TEM,FTIR和ESR对处理后的碳纳米管的形貌,官能团类型和电子自旋状态进行了表征。结果表明:酸处理能够切断碳纳米管,并且使其管径变小,同时可以使碳纳米管的C-C键发生断裂,产生-COOH。ESR图谱显示电子自旋谱的峰高比随酸处理时间增加而增加,意味着增加碳纳米管中未成对电子和导带电子数量有所增加。同时酸处理后的碳纳米管的g因子和线宽都随着酸处理时间增加而增加,g因子从2.012增加到2.018,线宽从19×10-4增加到26×10-4,意味着缺陷能够影响电子自旋状态。     

Study on n-type Doped Electron-Transporting Layers in OLEDs by Electron Spin Resonance

We present an electron spin resonance (ESR) study of Cs₂CO₃ and LiF doped tris(8-hydroxyquinoline) aluminum (Alq₃) thin films. The g values of the Cs₂CO₃ and LiF doped Alq₃ thin films were obtained as 2.0040 and 2.0028, repectively. The g value of the LiF doped film was very close to a theoretically calculated one for an isolated Alq₃ radical anion, while Cs₂CO₃ doped film showed a large g shift. This feature can be explained by large spin-orbit interaction caused by heavy Cs atoms. While doping of Cs₂CO₃ did not showed cathode-metal (Al and Au) dependence, LiF doping required Al as cathode.     

Overhauser Shift of the Conduction Electron Spin Resonance in (FA)2PF6 Single Crystals

The shift ΔB _ov of the ESR line due to saturation of the NMR of the hyperfine coupled nuclei (Overhauser shift) was measured for single crystals of the organic conductor (FA)₂PF₆. ΔB_ov , is proportional to [Abar] _tt , being the average hyperfine interaction between the conduction electrons and the protons in resonance, and the dynamic nuclear spin polarization (DNP), respectively. The DNP enhancement factor V was determined for the two orientations of the static magnetic field B _o , perpendicular (V _∥ = 525 ± 40) and parallel (V _∥ = 280 ± 25) to the needle axis a, respectively. The absolute value of the average hyperfine coupling is [Abar]^zz = –(1.16 ± 0.05) Gauss · g_e μ _B . Both, the temperature dependence and the anisotropy of the proton spin relaxation times T ₁ ^p and T ₁ ^p were measured from the time dependence of the Overhauser shift, ΔB_ov (t) after rf-pulses or after switching “on” and “off” the ESR saturation. Within the metallic phase of the crystal the proton relaxation is governed by a Korringa law. The experiments definitely show, that the electron spins, showing up in the ESR are those of the conduction electrons.     

Low-Temperature Electron Spin Resonance in (TMTSF)2PF6 in the High Pressure Metallic Phase

Abstract

The electron spin resonance of (TMTSF)₂PF₆ has been observed at low fields (H_o < 110 Oe) in the high pressure, metallic phase (p > 6.5 kbar) in the temperature range 1-4^?K. The anisotropy in the g value is similar to that observed at ambient pressure above the metal-insulator transition. The linewidth is very narrow and the spin susceptibility strongly decreases as the superconducting transition is approached from above. We interpret this as evidence for singlet-paired superconductivity. Superconductivity is observed at 1.1 K and the critical field has angular dependence in the be plane. These observations lead us to conclude that (TMTSF)₂PF₆ is a singlet paired superconductor.     

Electron Spin Resonance of K-Doped Single-Wall Carbon Nanohorns and Single-Wall Carbon Nanotubes

Abstract

K-doping into the aggregate of single-wall carbon nanohorns (SWNHs) and into the bundle of single-wall carbon nanotubes (SWNTs) are introduced in this study. Electron spin resonance (ESR) of the pristine SWNHs and SWNTs show that the pristine SWNHs are ESR active and the linewidth (ΔH) is susceptive to the partial pressure of O₂, while the pristine SWNTs are ESR silent. ΔH of K-doped SWNHs becomes wider by a factor of ?2 than that of the pristine one. For K-doped SWNTs, the Dysonian type ESR comes to be observed. Details of the ESR features are discussed.     

Orientation of Small Molecules in a Nematic Liquid Crystal as Studied by Electron Spin Resonance

Based on the measurements of hyperfine splitting constants (hfsc) of small aminoxyl (nitroxide) radicals in the nematic phase of N-4-methoxybenzylidene-4'-n-butylaniline (MBBA) we discussed the relation between the molecular orientation and the molecular shapes, especially the contribution of the phenyl groups to the molecular alignments.     

真空退火处理对纳米氮化硅电子自旋共振谱的影响

用微米级SiO2、Si和碳黑混合粉末为原料, 以氮气为反应气,采用碳热还原法合成了氮化硅纳米粉体.测量了300～1273K退火温度下纳米氮化硅的电子自旋共振(ESR)谱,研究了测量温度、纳米氮化硅退火温度对ESR谱线型、g因子、线宽的影响.结果证实退火影响纳米氮化硅的磁性.     

Magnetic Resonance Studies of Spin Dynamics in Trans-Polyacetylene

We present a study of the temperatue dependce of the spin dynamics in trans-polyacetylene using dynamic nuclear polarisation, nuclear relaxation and EPR measrements.     

Electron Spin Echo Study on Polyacetylene

Electron spin Echo (ESE) measurements on stretch-oriented films of polyacetylene are reported. The electron dipole-dipole interaction is estimated. Effect of oxygen on the phase memory decay has been studied.     

Microstructural Effects of Mn2+ ions in ZnO Nanoparticles

Semiconducting ZnO nanoparticles with manganese content 0 at. %, 5 at. % and 10 at. % were prepared by co‐precipitation technique and XRD reveals that the average crystallite size D is 10.2 nm, 7.62 nm and 7.06 nm respectively. The individual contributions of the size and strain to the XRD peak broadening were investigated by Williamson‐Hall (W‐H) analysis. The strain, stress and energy density were calculated more precisely by uniform deformation model (UDM), uniform stress deformation model (USDM), uniform deformation energy density model (UDEDM) and size‐strain plot (SSP) method. The average particle size from HRTEM analysis is 13 ± 2 nm. The evaluated average crystallite size from the W‐H analysis and SSP method is commensurate with the particle size from HRTEM. Diamagnetic to ferromagnetic phase transition observed is interpreted interms of the anisotropic strain due to the dopant.     

Electron Paramagnetic Resonance of VO2+ in M2Zn(SeO4)2 · 6H2O(M=K,Rb) Single Crystals

The EPR spectrum of VO²⁺ has been studied in single crystals of K₂Zn(SeO₄)₂ · 6H₂O and Rb₂Zn(SeO₄)₂ ∼ 6H₂O at ∼9.45 GHz. VO²⁺ substitutes for Zn²⁺ have preferential orientations in the lattice. The V = O of the intense vanadyl center is nearly along the longest Zn H₂O direction. Spin-Hamiltonian parameters have been evaluated from single crystal as well as from powder spectra.     

Glow Curves of Thermally Pretreated KCl:Mn2+ Crystals

Thermoluminescence studies of KCl crystals doped with 0.5 mole% of Manganese both in “as grown” state and after quenching them from various elevated temperatures indicate that the position of the glow peaks is found to depend upon the state of dispersion of impurity. In quenched crystals two additional peaks one around 130 and other around 215°C are observed. Dipoles near dislocations are suggested to be responsible for 130°C peak and 215°C peak to a complex formed by the associated of one or more Mn²⁺ ions with a single vacancy or an aggregate of vacancies, the complex being situation in the dislocation region.     

Dephasing of Electron Spin Echo in the Triplet State of Orientationally Disordered Crystals

Conventional and pulse optically detected magnetic resonance spectroscopy is used to study the dynamics of electronic energy transfer process in two orientationally disordered crystals, 1-bromo-4-chloronaphthalene and 4-bromo-4'-chlorobenzophenone.     

一种异极矿仿制品—钠硅灰石微晶玻璃的研究

借助光学显微镜和、扫描电镜、X射线粉晶衍射仪和电子探针等仪器设备,对异极矿仿制品的物理光学特征、内部结构、物相组成以及化学成分等方面进行了详细的研究.结果表明:研究样品为块状钠硅灰石微晶玻璃,浅绿蓝色到蓝色,可见白色点状物和表面孔洞,玻璃光泽,半透明至微透明,斑状结构,内部可见针状、柱状晶体以及扫帚状晶体集合体,折射率1.51,比重2.49.在物理光学参数和内部结构方面与异极矿都有一定的差异.钠硅灰石微晶玻璃的原始材料属于Na2O-CaO-SiO2成分体系或Na2O-CaO(MgO)-SiO2成分体系,并含有少量的Al2O3和CuO,采用烧结法制备而成,其浅绿蓝色到蓝色的色调是Ca2和Fe3+的综合作用的结果.     

EPR studies on Mn2+ centres in solid solutions of TSCC and TSCB

EPR investigations of Mn²⁺-doped solid solutions of TSCC and TSCB were performed between 130 K and 300 K. The axial fine structure parameter D vs bromine concentration x is nonlinear. The relation between the axial fine structure parameter and bromine concentration is discussed by means of a simple statistical model.