共查询到20条相似文献,搜索用时 15 毫秒
1.
Josep Batle Ahmed Farouk Majid Alkhambashi Soliman Abdalla 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(3):49
Quantum correlations are generally impossible to address directly in bulk systems. Quantum measures extended only to a few number of parties can be discussed in practice. In the present work we study a cluster of spins belonging to a compound whose structure is that of a quantum magnet. We reproduce at a much smaller scale the experimental outcomes and then we study the role of quantum correlations there. A macroscopic entanglement witness has been introduced in order to reveal quantum correlations at nonzero temperatures. The critical point beyond which entanglement is zero is found at T c = 15 K. 相似文献
2.
The [N(CH3)4][N(C2H5)4]ZnCl4 compound has been synthesized by a solution-based chemical method. The X-ray diffraction study at room temperature revealed
an orthorhombic system with P21212 space group. The complex impedance has been investigated in the temperature and frequency ranges 420–520 K and 200 Hz–5 MHz,
respectively. The grain interior and grain boundary contribution to the electrical response in the material have been identified.
Dielectric data were analyzed using the complex electrical modulus M
* for the sample at various temperature. The modulus plots can be characterized by full width at half height or in terms of
a non-exponential decay function ϕ(t) = exp[(−t/τ)
β
]. The detailed conductivity study indicated that the electrical conduction in the material is a thermally activated process.
The variation of the AC conductivity with frequency at different temperatures obeys the Almond and West universal law. 相似文献
3.
Molecular structure of tris(acetylacetonato)scandium, Sc(C5H7O2)3, is investigated by gas-phase electron diffractometry. The main structural parameters of the molecule are evaluated. The
average intemuclear distances and angles correspond to C3 symmetry. The chief structural motif is trigonal antiprisms of six oxygen, carbon, and hydrogen atoms with a scandium atom
at the center. It is found that rg[Sc-O) = 204.1(8) pm and rg(C−O) = 124.7(4) pm
Translated fromZhurnal Struktumoi Khimii, Vol. 39, No. 4, pp. 633–639, July–August, 1998. 相似文献
4.
R. B. Morgunov E. V. Kurganova S. M. Aldoshin N. A. Sanina T. N. Rudneva 《Physics of the Solid State》2007,49(9):1723-1730
The magnetic properties of the binuclear nitrosyl-iron complexes Fe2(SC3H5N2)2(NO)4 are investigated. It is demonstrated that several types of particles, such as dimers with a pair of spins 1/2, dimers with a pair of spins 5/2, and paramagnetic particles with spin 3/2, make a contribution to the magnetic properties of the complexes. A decrease in the temperature below 25 K leads to a change in the shape of the EPR spectra corresponding to these dimers, so that Lorentzian lines (homogeneous broadening) transform into Gaussian lines (inhomogeneous broadening). This is accompanied by a stepwise change in the EPR line width and g factors. The change in the line shape indicates that complexes become asymmetric at low temperatures, possibly, due to the decrease in the spin exchange frequency below the frequency of the microwave field of the spectrometer. 相似文献
5.
The results of x-ray structural studies of the [N(C2H5)4]2CdBr4 crystal at low temperatures are presented. The unit cell parameters and the thermal expansion coefficients along the main crystallographic directions are measured at temperatures in the range from 90 to 320 K. The integrated intensities of the diffraction reflections are investigated as a function of the temperature. It is shown that the curves a = f(T), c = f(T), I 500 = f(T), and I 006 = f(T) at temperatures T 1 ≈ 174 K and T 2 ≈ 226 K exhibit anomalies in the form of abrupt changes in the lattice parameters and the diffraction reflection intensities. This indicates that the [N(C2H5)4]2CdBr4 crystal undergo phase transitions at these temperatures. Moreover, there is an anomaly in the form of a small maximum at the temperature T 3 = 293 K. 相似文献
6.
Three different photomagnetic effects caused by ultraviolet light in paramagnetic crystals based on molecules of spiropyrans
(Sp) Sp3Cr(C2O4)3 and SpI have been revealed and separated: (1) in the high-temperature range (30–300 K), the photomagnetic effect in Sp3Cr(C2O4)3 is determined by the charge transfer between chromium ions and spiropyran molecules; (2) in the low-temperature range (2
K), the photomagnetic effect in Sp3Cr(C2O4)3 is due to the photoisomerization of spiropyran molecules, the change in the crystal field, and the splitting of the levels
of Cr3+ ions in zero field; and (3) in the temperature range 2–20 K, the generation of radiation-induced paramagnetic defects contributes
to the magnetic moment of the organic sublattice Sp+. 相似文献
7.
The temperature dependence of the electrical conductivity of the compound 2,4,4-trimethyl-4,5-dihydro-3H-benzo[b] [1,4] diazepin-1-ium tetrachlorocadmiate in the different phases follows the Arrhenius law. The imaginary part of
the permittivity constant is analyzed with the Cole–Cole formalism. In the temperature range 348–394 K, the activation energy
of conductivity obtained from complex permittivity in regions I and II are, respectively, 1.03 and 0.33 eV, and E
m (in regions I and II are, respectively, 0.97 and 0.36 eV) obtained from the modulus spectra is close, suggesting that the
ion transport is probably due to a hopping mechanism. The Kohlrausch–Williams–Watts function,
j(t) = exp( - ( \fractt\textKWW )b ) \varphi (t) = \exp \left( { - {{\left( {\frac{t}{{{\tau_{\text{KWW}}}}}} \right)}^\beta }} \right) , and the coupling model are utilized for analyzing electric modulus at various temperatures. The decreasing of β at 373 K is due to approaching the temperatures of change in the conduction mechanism of the sample. 相似文献
8.
9.
F. B. Mushenok A. I. Dmitriev M. V. Kirman S. M. Aldoshin N. A. Sanina R. B. Morgunov 《Physics of the Solid State》2010,52(10):2135-2141
Ordered arrays of nanowires of the photochromic antiferromagnet SpFeMn(C2O4)3 (where Sp is 1-{(1′,3′,3′-trimethyl-6-nitro-5′-chlorospiro[2H-1-benzopyran-2,2′-indolin]-8-yl)methyl}pyridinium) have been fabricated in anodized aluminum oxide pores with diameters of
20 and 200 nm. It has been revealed that the growth of the spin-glass phase with noncollinear ordering of spins in nanowires
is suppressed in favor of the uniaxial antiferromagnetic phase. A decrease in the nanowire diameter leads to an increase in
the anisotropy of the magnetic resonance spectra. This is associated with the magnetocrystalline anisotropy that considerably
exceeds the anisotropy of the nanowire shape. 相似文献
10.
Q. Ren X. Q. Wang H. L. Yang G. H. Zhang X. B. Sun W. F. Guo F. J. Zhang X. Zhang Y. T. Chow D. Xu 《Laser Physics》2007,17(8):1058-1061
A novel dmit organometallic complex—[(C4H9)4N][Co(dmit)2] (dmit2? = 4,5-dithiolate-1,3-dithiole-2-thione), abbreviated as BuCo, is synthesized and its third-order optical nonlinearity of the acetone solution is characterized using the Z-scan technique with a 40-ps pulse width at 1064 nm. Z-scan curves show that BuCo sample solution possesses the negative nonlinear refraction, exhibiting a self-defocusing effect. In addition, the two-photon absorption has been observed in BuCo. The effective molecular second-order hyperpolarizability γeff of the BuCo molecule was estimated to be as large as 5.60 × 10?31 esu, suggesting BuCo is a potential material for optical device applications. 相似文献
11.
S. O. Adamson 《Russian Journal of Physical Chemistry B, Focus on Physics》2016,10(1):143-152
The stationary points of the potential energy surfaces for the reactions C2H2 + OH and C2 + H2O are calculated using density functional theory and the coupled cluster method. The relative energies and geometric parameters of the stable intermediates and transition states are in good agreement with the results of independent studies. In most cases, the relative energies differ from the earlier published values by no more than 3 kcal/mol, whereas the rotational constants, by 1–2%. The mechanism of the reaction CCOH2 → C2 + H2O is studied in detail. The possible sources of errors in the calculation methods are examined. 相似文献
12.
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
13.
The Rb3(HSeO4)2.5(H2PO4)0.5 compound was prepared and its thermal behavior and electric properties were investigated. The thermogravimetry (TGA) analysis and the differential scanning calorimetric (DSC) show the presence of a structural phase transition of the title compounds at 374 K which is confirmed by the variation of fp and σdc as a function of temperature. The complex impedance of the Rb3(HSeO4)2.5(H2PO4)0.5 compound has been investigated in the temperature range of 295–453 K and in the frequency range 209 Hz–1 MHz. The impedance plots show semicircle arcs at different temperatures, and an electrical equivalent circuit has been proposed to explain the impedance results. The circuits consist of the parallel combination of bulk resistance Rp and constant phase elements CPE1 in series with fractal capacity CPE2. The frequency dependence of the conductivity is interpreted in terms of Jonscher’s law. The conductivity dc follows the Arrhenius relation. The near value of activation energies obtained from the analysis of modulus, conductivity data, and circuit equivalent confirm that the transport is through the ion hopping mechanism, dominated by the motion of the H+ proton in the structure of the investigated materials. 相似文献
14.
Effects of a mechanical shear on the electron transport properties of a (LaMnO3)2/(SrMnO3)2 superlattice are investigated using first-principle DFT calculations. While the unstrained superlattice is a 3-D conducting
half metal, application of a pyramidal shear transforms it into a non-spin-polarized conductor. Depending on whether the out-of-plane
component of the shear is tensile or compressive the conductivity is 1-D out-of-plane or 2-D in-plane. The shear-induced low-dimensional
conductivity is also associated with the FM-AFM transition. 相似文献
15.
R. B. Morgunov F. B. Mushenok S. M. Aldoshin N. A. Sanina 《Journal of Experimental and Theoretical Physics》2009,109(4):667-675
The effect of irradiation by ultraviolet light on the effective magnetic moment of a paramagnetic single crystal based on
photochrome spiropyran (Sp) and chromium oxalates Sp3Cr(C2O4)3 molecules is detected. It is shown that the deviation of the temperature dependence of the magnetic moment from the Curie
law is caused not by the exchange interaction, but by electron redistribution between Cr3+ and Cr4+ ions and spiropyran molecules Sp0 and Sp+. Analysis of the angular dependence of EPR spectra makes it possible to determine the contribution of Cr3+ ions to the magnetic properties of the crystals and to determine the crystal field parameters D = 0.619 cm−1 and E = 0.024 cm−1. Irradiation of hydrated samples by ultraviolet light leads to intensity redistribution of EPR lines attributed to Cr3+ and Sp0. Thermally stimulated paramagnetism of triplet states of spiropyran ions Sp+ and the SpI salt is observed. 相似文献
16.
The Gross-Pitaevski equation modified through the inclusion of a term accounting for the nonlocality of interatomic interaction was used to demonstrate the occurrence of extremely narrow two-and three-dimensional solitonic states in atomic Bose-Einstein condensates. The estimates of the sizes of these states gave a value of ~ 20–60 nm (atomic “needles” and “bullets”) for lithium atoms. The soliton lifetimes caused by two-and three-particle collisions were estimated. The limiting possibilities of the formation of nanostructures using needles and bullets were compared with the possibilities of other nanolithographic methods. 相似文献
17.
S. V. Mel’nikova A. S. Krylov A. L. Zhogal’ N. M. Laptash 《Physics of the Solid State》2009,51(4):817-822
Polarization-optical study of twinning and measurements of the Raman spectra and birefringence in oxyfluoride (NH4)3Ti(O2)F5 were carried out over the temperature range 90–350 K. Phase transitions were detected at temperatures T 01 = 266 K (second-order transition) and T 02 = 225 K (first order). It is assumed that the crystal symmetry is changed as follows: Fm3m ? I4/mmm ? I4/m. Anomalies of the spectral parameters are established in the frequency range of internal vibrations of ammonium ions and Ti(O2)F5 complexes. An analysis of the results shows that the transition at T 01 is likely due to small shifts of the tetrahedral groups from their position on the triad axis and that the transition at T 02 is due to fluorine-oxygen ordering of Ti(O2)F5 complexes. 相似文献
18.
The Ac electrical conductivity and the dielectric relaxation properties of the [(C3H7)4N]2Cd2Cl6 polycrystalline sample have been investigated by means of impedance spectroscopy measurements over a wide range of frequencies
and temperatures, 209 Hz–5 MHz and 361–418 K, respectively. The purpose is to make a difference between the electrical and
dielectric properties of the polycrystalline sample and single crystal. Besides, a detailed analysis of the impedance spectrum
suggests that the electrical properties of the material are strongly temperature-dependent. Plots of (Z" versus Z') are well
fitted to an equivalent circuit model consisting of a series combination of grains and grains boundary elements. Moreover,
the temperature dependence of the electrical conductivity in the different phases follows the Arrhenius law and the frequency
dependence of σ (ω) follows the Jonscher’s universal dynamic law. Furthermore, the modulus plots can be characterized by full
width at half height or in terms of a nonexperiential decay function φ(t) = exp(t/t)β. Finally, the imaginary part of the permittivity constant is analyzed with the Cole–Cole formalism. 相似文献
19.
We have carried out experimental and theoretical
studies on electron scattering from the C3H6 isomers and
C3F6 molecules and we report on total, differential as well
as theoretical integral elastic cross-sections for these
molecules. Vibrational excitation functions are also presented for
the typical vibrational peaks in C3H6 and cyclo-C3H6
for the angle of 90○, impact energy range of 1–16 eV
and loss energies of 0.12 eV and 0.13 eV, respectively. In the
cross-sections, clear differences in peak positions and magnitudes
between the C3H6 isomers can be viewed as the isomer effect.
The same is observed between C3H6 and C3F6 in a clear
manifestation of the fluorination effect. The resemblance of the
π* shape resonance in the cross-sections, observed at about
2.2 eV for C3H6 and 3.5 eV for C3F6, to those in
C2H4 and C2F4 clearly points to the effect of the
double bond in the molecular structures for these molecules.
Theoretical analysis is performed to provide rationales for the
scattering dynamics. 相似文献
20.
In an EPR study of the catalytic system TiCl4 + Al(i-C4H9)3 in toluene and isopentane in TiCl4/oligopiperylene + Al(i-C4H9)3 in toluene, we have observed a dependence of the linewidth of the hyperfine structure on the mobility of the complex in solution.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 174–177, March–April, 2007. 相似文献