共查询到20条相似文献,搜索用时 15 毫秒
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K. P. Meletov 《Physics of the Solid State》2014,56(8):1689-1695
Raman spectra of crystals of the molecular fullerene C60 donor-acceptor complex {Hg(dedtc)2}2 · C60 (fullerene with mercury diethyldithiocarbamate) have been measured at a pressure up to 8.4 GPa and at room temperature. A phase transition has been revealed in the pressure range of 1.2–2.0 GPa, which is accompanied by a splitting of the degenerate intramolecular phonon modes H g (1)-H g (4) and H g (7)-H g (8), as well as by a softening of the H g (2) mode of the fullerene C60. As the pressure further increases to the maximum value, the intensity of the bands varies smoothly. A decrease in the pressure leads to the reverse transition to the initial state at 1.2 GPa. The splitting of the degenerate modes H g (1)-H g (8) and the softening of the H g (2) modes resemble their behavior in the formation of dimers in fullerite crystals and indicate the possible formation of dimers in two-dimensional fullerene layers under hydrostatic compression of the {Hg(dedtc)2}2 · C60 complex. 相似文献
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The magnetic properties of the single crystalline Mn(2)AS(4) (A = Si and Ge) with an olivine structure, which are the uniaxially anisotropic antiferromagnets (the b axis as an easy axis), were investigated. Near the Néel temperature, both compounds exhibit the contrastive magnetic responses along the c axis, namely, the spontaneous weak ferromagnetism in A = Si and the significant enhancement of the differential susceptibility (dM/dH) under the small magnetic field in A = Ge. When A = Ge, we also observed the evolution of dM/dH along the axis at low temperatures. We discuss these phenomena on the basis of the magnetic field-temperature (H-T) phase diagram with the spin-flop bicritical point (H(BP), T(BP). The role of the thermal or quantum fluctuation was stressed. 相似文献
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In strong magnetic field and at low temperature, 2-D electron systems are expected to show distinctive temperature oscillations when the field is changed adiabatically. 相似文献
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T. I. Arbuzova S. V. Naumov V. L. Arbuzov A. P. Druzhkov 《Physics of the Solid State》2009,51(5):953-960
The influence of radiation defects on the magnetic properties of polycrystalline CuO and a high density nanoceramic with crystallite sizes d = 5 and 15 nm has been studied in the temperature range T = 77–300 K. Electron irradiation at fluences Φ = 5 × 1018 cm?2 initiated an increase in the susceptibility χ ~ 1/T below 150 K, a feature anomalous for 3D antiferromagnets. The nonlinear behavior of magnetization in weak fields, the increase in the magnetic moment with decreasing temperature, and observation of the spontaneous magnetic moment at temperatures T < 150 K can be attributed to local changes in the exchange parameters and the formation of clusters with uncompensated magnetic moments in the antiferromagnetic matrix near point defects. 相似文献
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N. G. Spitsina V. V. Gritsenko O. A. D’yachenko É. B. Yagubskii 《Physics of the Solid State》2002,44(3):531-533
A new molecular C60 complex of the composition (BMDT-TTF) · C60 · 2CS2 (I) with the bis(methylenedithio)tetrathiafulvalene (BMDT-TTF) organic donor is synthesized. The molecular and crystal structures of this complex are determined by x-ray diffraction. The (BMDT-TTF) · C60 · 2CS2 (I) compound crystallizes in a monoclinic crystal system. The main crystal data are as follows: a=13.550(5) Å, b=9.964(7) Å, c=17.125(8) Å, β=99.52(4)°, V=2280(2) Å3, M=1229.45, and space group P21/m. Crystals of I have a layered structure: layers consisting of C60 molecules alternate with layers composed of BMDT-TTF and CS2 molecules. It is found that, in complex I, the donor and C60 molecules are linked through the shortest contacts, which leads to a change in the molecular geometry of BMDT-TTF. The donor molecules in a crystal layer are characterized by the shortest S...S contacts. The IR data indicate the electroneutrality of the fullerene molecule. The electrical conductivity of (BMDT-TTF) · C60 · 2CS2 single crystals is measured using the four-point probe method at room temperature: σRT=2×10?5 Ω?1 cm?1. 相似文献
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E. P. Naiden 《Russian Physics Journal》2007,50(2):170-176
The phase composition, structure parameters, and basic magnetic properties of several magnetically alloyed spinel-ferrite
nanopowders produced from salt solutions are studied. Particle-size and surface effects on the saturation magnetization and
magnetic anisotropy of the examined materials are investigated. The validity of the core-shell model for describing the magnetic
properties of the nano-sized spinel ferrites under review is discussed.
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Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 2, pp. 66–72, February 2007. 相似文献
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S. Jaksch I. M?hr S. Denifl A. Bacher O. Echt T. D. M?rk P. Scheier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,52(1-3):91-94
Helium nanodroplets, formed in a supersonic expansion, are doped with C60 in a pickup cell. In some experiments, they are co-doped with water. Electrons are attached to the doped droplets; the yield of anions is recorded as a function of electron energy. The C60 - yield extends to much higher energies than in experiments involving isolated, hot fullerenes; we attribute the difference to the low temperature of the neutral precursors and the efficient cooling of the nascent anions by the helium droplet, which quench thermally activated autodetachment. The yields of (C60)2 - and C60D2O- anions reveal another important factor, namely depletion of the anion signal by dissociation which is energetically more facile than autodetachment. 相似文献
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V. Brouet H. Alloul E. Lafontaine L. Malier L. Forro 《Applied Physics A: Materials Science & Processing》1997,64(3):289-293
\chem{Cs_{1}C_{60}} . The NMR spectrum allows, when the Magic Angle Spinning (MAS) technique is used, to get information about the electronic structure
of this phase, which points out that the spin density is not uniformly distributed on the ball. An estimation of the strength of the quadrupolar effects on is then given, which shows that it is possible to analyse the spin-lattice relaxation time in terms of magnetic effects. A comparison with the of is then justified and allows us to point out the importance of low dimensional antiferromagnetic fluctuations in this compound.
We also investigate the nature of the magnetic ground state in : the broadening of the spectra states unambiguously its magnetic nature and a detailed analysis of their shape gives further
indications on the antiferromagnetic nature of the magnetic order, which seems characterized by a large amount of disorder.
Received: 19 November 1996/Accepted: 19 December 1996 相似文献
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R. Ludeke 《Solid State Communications》1977,24(10):725-728
We have observed a unique, pressure-dependent adsorption isotherm of oxygen on the ZnSe (100) surface, which consists of an unmeasurable uptake followed by an irreversible, step-like uptake for pressures exceeding a critical value of ~ 0.08 torr at room temperature. A partial depletion of Se accompanies this adsorption process. For incomplete oxidation, oxygen induced (2 × 1) and (3 × 1) surface reconstructions may be generated, the first such structures to be observed for semiconductors. The electron-energy-loss spectra for these surfaces and for the clean ZnSe (100)c(2 × 2) surface are presented. The clean surface exhibits a dangling-bond-derived empty surface state ~ 1 eV above the conductor band edge, and filled surface states near 3.2, 6.5, and 15 eV below the valence band edge. 相似文献
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We have observed the formation of C2-60 and C2-70 in collisions between C(-)(60)/C(-)(70) and Na atoms. Cross sections for the electron transfer to the monoanion are determined to be 36+/-9 and 57+/-14 A(2) for C-60 and C-70, respectively. A simple model investigation suggests that the electron is transferred from a Na atom to a low-lying electronic state of the fullerene to form a dianion. The method leads to pico-ampere energetic beams of C60 dianions that can be used for spectroscopy and lifetime studies. 相似文献
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The temperature dependence of the surface resistivity for a metallic K(3)C(60) ordered film in the nonsuperconducting state has been obtained by reflection electron energy loss spectroscopy. We demonstrate that the normal state electronic and transport properties of the top molecular layer of K(3)C(60) are similar to the corresponding properties measured with bulk sensitive techniques. These observations strengthen and give a general character to the experimental results obtained with surface sensitive techniques on fullerene compounds. In addition, the transport properties may deviate from the Fermi-liquid behavior above 500 K. 相似文献
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Y. Suezaki 《Physics letters. A》1972,40(5):419-420
By introducing the alternant site energy ε0, a Schottky type behavior of the magnetic susceptibility is also obtained in the case of a 4-site 2-electron ring Hubbard model which is the model for TCNQ complex salts. 相似文献
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We present high resolution heat capacity measurements of the organic superconductors kappa-(ET)(2)Cu[N(CN)(2)]Br and kappa-(ET)(2)Cu(NCS)(2) in fields up to 14 T. We use the high field data to determine the normal state specific heat and hence extract the behavior of the electronic specific heat C(el) in the superconducting state in zero and finite fields. We find that in both materials for T/T(c) less or similar 0.3, C(el)(H=0) approximately T2 indicating d-wave superconductivity. The data are well described by a strong coupling d-wave model from our base temperature (T/T(c) approximately 0.1) right up to T(c). Our data help to resolve the controversy regarding the order parameter symmetry in these materials. 相似文献