共查询到20条相似文献,搜索用时 31 毫秒
1.
Spin lattice relaxation T1 of naturally abundant 13C nuclei in squaric acid was measured close to the antiferroelectric-paraelectric phase transition temperature Tc = 373 K. A rapid increase in is observed close to Tc coming from above, which follows the power law where . This behaviour is explained on the basis of the two-dimensional character of the fluctuations. 相似文献
2.
We have determined the behavior of the density of states in the mixed state of superconducting alloys for T → Tc. The local density of states tends towards the BCS expression with the order parameter playing the role of the energy gap. The singularities are smeared out by the spatial average. The effective normal core radius of a vortex diverges like for T → Tc unlike the coherence length which diverges like . 相似文献
3.
Anil K. Bhatnagar B. Bhanu Prasad N. Ravi R. Jagannathan T.R. Anantharaman 《Solid State Communications》1982,44(6):905-909
Amorphous Fe40Ni40B20 (VITROVAC 0040) alloy has been investigated using 57Fe Mössbauer Spectroscopy. The Curie temperature Tc is found to be well defined and is 695 ± 1 K. The quadrupole splitting just above Tc is 0.64 mm sec?1. The crystallization temperature is 698 ± 2 K, close to but definitely above Tc. The average hyperfine field Heff(T) of the glassy state shows a temperature dependence of indicative of the existence of spin wave excitations. The values of and are found to be 0.40 and 0.06, respectively, for T/Tc ? 0.72. At temperatures close to Tc, Heff(T) varies as (1 ? T/Tc)β where β is one of the critical exponents and its value is found to be 0.29 ± 0.02. 相似文献
4.
We studied the energy width and the width in reciprocal space Δq of the central mode of SrTiO3 above Tc. At Tc+4° we observed an energy width of about 6×10?7 eV. If the measured Δq is interpreted by a correlation length we obtain . 相似文献
5.
Tc measurements for V1?xTixHy show that a decrease in Tc always occurs upon hydrogenation, but with slopes ( that change with x. A phenomenological model is suggested, associating the Tc decrease in most of the range of x to changes in nominal number of conducting electrons and in the volume induced by the hydrogenation. The model roughly accounts for the variations in Tc in the V-rich alloys. It fails to explain the Tc variation at the Ti end. 相似文献
6.
7.
Measurements of the temperature and pressure dependences of the resistivity of the pseudo-one-dimensional ternary compound Tl2Mo6Se6 are presented. We find that the conductivity parallel to the highly conducting c-axis is enhanced by pressure and the superconducting transition temperature Tc is suppressed by pressure at a rate kbar?1. These results are discussed in relation to the current models of transport in one-dimensional conductors. 相似文献
8.
The Josephson current for an anisotropic superconductor, described by Shiba-Rusinov model, containing paramagnetic impurities is calculated by an extension of the theory of Nagi and Upadhyayya. The slope of against temperature T near Tc is also computed and compared with the limiting isotropic case. Thermodynamic critical field for an anisotropic superconductor is also investigated. 相似文献
9.
The temperature dependence of the critical value κc of the Ginzburg-Landau parameter which separates type-II/1 from type-II/2 superconductors is theoretically computed by means of a microscopic calculation of the boson characteristic function at nonzero temperature, assuming that the temperature is not too close to Tc. Agreement with experimental data is satisfactory in the region . 相似文献
10.
In the critical region of the insulating, uniaxial ferromagnet GdCl3 the real part of the uniform susceptibility χ(q = 0, ω; T) has been measured by means of a frequency counting method in the ranges . Parallel to the easy direction at all temperatures, χ′(ω) has a lorentzian shape, its amplitude being equal to the static susceptibility, χT. The half-widths τ?1 exhibit s critical slowing down: above ?c = 0.03 they are proportional to χ?1T, while at ?c a change-over to occurs, the origin of which is uncertain. 相似文献
11.
M.D. Pollock 《Nuclear Physics B》1982,208(1):182-188
It is known that a scalar field that is non-minimally coupled to the geometry implies a varying gravitational “constant” Geff, and hence a violation of the continuity equations, , where is the uncorrected energy-momentum tensor. This in turn upsets classical thermodynamics. 3he simplest resolution of this difficulty is to multiply all energetic quantities by , where GN is the newtonian gravitational constant. This modified thermodynamics is applied to the scalar-field version of the cosmological model of Zee, for which it is shown to cause restoration of the symmetry above some critical temperature Tc close to the Planck temperature. We also illustrate how the second law of thermodynamics is always obeyed, correcting a recent discussion by Davies. 相似文献
12.
Measurements of the temperature dependence of the upper critical field, Hc2(T), for a series of V100?xGax materials are presented for 20.5 ≤ × ≤ 29.6. Fits of the data to conventional theory for a paramagnetically limited, dirty, type II superconductor show: 1) a maximum in Tc and Hc2(0) for x ? 25; 2) a constant ( for x ≤ 25; 3) a slowly increasing value of λso with increasing x up to x ~ 25; and 4) good agreement with stoichiometric ordered and thermally disordered V3Ga. Above broader transitions are observed. For x = 25, Tc = 15.3 K, (, λso = 0.3 and Hc2(0) = 23.4 tesla. The effects of inclusion of strong-coupling in the theory are discussed briefly. 相似文献
13.
W. Windsch H. Braeter U. Gutteck B. Malige B. Milsch 《Solid State Communications》1982,42(12):839-842
The concentration dependence of the ferroelectric transition temperature Tc of single crystals of the solid solution tris-sarcosine calcium chloride1?x bromidex is studied experimentally by measurement of the static dielectric constant ?b and described by the empirical relation . The Ising model with transverse field and the model of coupled anharmonic oscillators are used to explain the concentration dependence of the transition temperature Tc. 相似文献
14.
We have carried out a high-resolution X-ray critical scattering experiment in the isotropic phase connected with the isotropic-smectic-B transition in 4,4-di-n-hexyl-biphenyl. The measurements yield the following parameter values: , and the critical exponents γ = 1.51 ± 0.12, ν∥ = 0.65 ± 0.06, ν⊥ = 0.70 ± 0.08. At the temperature t = 10?3 () the correlation lengths are and . 相似文献
15.
I.V. Ajinenko Y.A. Belokopitov P.V. Chliapnikov L.N. Gerdyukov V.V. Kniazev A.I. Kurnosenko A.K. Likhoded V.M. Perevoztchikov V.N. Riadovikov A.M. Rybin O.G. Tchikilev V.F. Tchunikhin V.A. Uvarov A.P. Vorobjev 《Nuclear Physics B》1980,176(1):51-60
The inclusive production of and Ξ? hyperons is investigated in K+ p interactions at 32 GeV/c. The production cross sections, 36.4±9 μb for the and 6.5±3 μb for the Ξ?, are rising strongly with energy similarly to and Λ production in K+ p interactions. The are produced preferentially in the forward direction in the c.m.s., while the Ξ? are produced dominantly backwards. The average transverse momenta and 〈pT〉Ξ?=0.58±0.09 GeV/c. 相似文献
16.
J. Ramakrishnan Robert J. Hardy George C. Kennedy 《Journal of Physics and Chemistry of Solids》1979,40(4):297-303
High pressure values for the adiabatic pressure derivative of temperature have been obtained by measuring the temperature change caused by a small rapid increase in pressure. Values for KBr and RbCl in phases B1 and B2 and for Bi in phases I, II and III are given for T = 295 K. The Grüneisen parameter γ is given by where Bs is the adiabatic bulk modulus. Ultrasonic and statk compressibility data are used to estimate the pressure and phase dependence of Bs. Dramatic increases in both γ and (?T/?P)s are observed as the pressure increases through a phase transition. Values for the logarithmic derivate are given. 相似文献
17.
L.R. Testardi 《Solid State Communications》1975,17(7):871-874
The temperature dependence of the superconducting critical current density Jc(T) in zero applied field from 4.2 K to Tc has been measured for 15 films of Nb-Ge with varying composition, deposition conditions, and radiation damage. The results show (i) the enhanced superconductivity observed in stoichiometric Nb3Ge as well as nonstoichiometric films is “bulk like” rather than filamentary, (ii) a simple correlation of the form which is reasonably independent of how the Tc has been achieved, and (iii) some additional evidence that the enhanced Tc of the films is not due to their chemical composition alone. 相似文献
18.
Taisuke Nakanaga Shigeo Kondo Shinnosuke Saëki 《Journal of Molecular Spectroscopy》1980,81(2):413-423
The Coriolis interactions between ν1 and ν3, and between ν2 and ν3 in SO2 have been analyzed to obtain the signs of the products and . It has been found that both of the signs of these products are positive. Then, relative signs of () have been determined using the calculated values of the Coriolis zeta constants for the present definition of the normal coordinates. The obtained sign combination of () is ±(+?+), which agrees with the one predicted by the molecular orbital calculations. Using the sign combination (+?+), the polar tensors of S and O atoms were also calculated. 相似文献
19.
We present approximate analytic calculation of the functional derivative , where Tc is the superconducting critical temperature and is the electron-phonon spectral function, within the “square-well model” for the phonon mediated electron-electron interaction and weak coupling limit is the Debye energy). It is found that where λ is the familiar electron-phonon coupling parameter and is a universal function of the reduced frequency . We compare this formula with accurate numerical results for several weak coupling superconductors. The overall agreement is good 相似文献
20.
Electron spin resonance relaxation times were measured for the radiation induced radical ion SeO43? in selenium doped KDP single crystals. The spin-lattice relaxation time was found to obey the relation from 7 K to 200 K except in the neighborhood of the transition temperature where the data fit the expression T1?1 = T1R?1b±T ? Tcm± where θ is the Debye temperature and the plus and minus signs refer to data at temperatures above and below Tc respectively. 相似文献