The Glauber dynamics of an Ising spin glass with infinite-range interactions and additional static field, h, is investigated near the freezing temperature, Tf. We obtain critical slowing down at and below the de Almeida-Thouless instability line, hc(T), to order (1?T/Tf)3 with algebraic decay of the spin correlations ~t?ν, where at Tf and for T<Tf. 相似文献
A detailed study of the electrical resistance, R(T), of a c-axis single crystal of holmium has been made in the vicinity of its Néel point. The results suggest that the critical temperature dependence of is determined by short range correlations for both T → T-N and T → T+N, although long range correlations become important in the paramagnetic state. 相似文献
New measurements are reported of the magnetic susceptibility above the freezing temperature Tf for noble-metal spin-glasses with to 6 at.% Fe or Mn. The susceptibility for Tf<T?5 Tf is not Curie-Weiss, but local magnetic correlations manifest themselves and provide a key for the determination of the exchange interactions in spin-glasses. The exchange parameters Jn are resolved up to 5 neighbors for Fe, Mn, Mn and Mn through a configuration ensemble calculation which includes atomic short range order. 相似文献
Correlations are deduced for the asymmetry and the halfwidth of a signal peak which correspond to a discrete level using different “isothermal” trap spectroscopy techniques. Using only the temperature of the scan peak maximum and the halfwidth δ = T2 ? T1 the activation energy can then be determined: , where TK(=4500?6000 KeV-1) is given numerically for certain frequently applied trap spectroscopy techniques. TK is the result of a complete mathematical treatment of the kinetic equation. 相似文献
A cosmological model is constructed which is a Friedman model, but with a finite ultimate temperature (TF). A plausible argument is presented which suggests that the existence of TF and the cosmic microwave background restricts the form of the hadronic level density: , where A, B = constants. In our model, integer. The case is the well-known Hagedorn model; the Frautschi model corresponds to s = 6 (B = 3); the cases and s = 2 (B = 2) have not been considered before now. For each value of , the model gives the temperature (Tγ0) of the microwave background as a function of A, TF and ?0 (the present energy density of the universe). Two fascinating results then emerge: first, all estimates of Tγ0 favor a low density Friedman universe (?0 = 10?31g/cm3), which rules out a universe with positive curvature; second, for ?0 = 10?31gr/cm3 the best estimate of Tγ0 (?3K) occurs for the Hagedorn model. 相似文献
The specific heats of the nearly one-dimensional antiferromagnet TMMC showed a sharp discontinuity in the temperature range ?(≡∥1?T/TN∥) ≈ 2 × 10-3 at TN =0.835 ± 0.010 K. The remaining magnetic entropy below TN is about 1% of its total for S = . 相似文献
The forced volume magnetostriction has been measured as a function of composition and temperature in amorphous (Fe1?xCox)90Zr10 alloys. The maximum value of (T = 0 K), equal to 285 × 10-10 Oe-1, has been observed for Fe90Zr10 alloys. The effect of pressure on the magnetization σ0 at T = 0 K was calculated from data. The pressure dependence of the Curie temperature Tc and σ0 behaves in a similar way as those observed for crystalline NiPd and NiRh alloys. 相似文献
The optical linear magnetic birefringence of single-domain NiO crystals was measured at temperatures above and below the antiferromagnetic phase transition. The analysis of the experimental data yield a Néel temperature of TN = (523.7 ± 0.2)K and a critical exponent β = 0.325+0.01-0.02 which determines the temperature behaviour of the magnetic long range order parameter . This critical behaviour of S? is found to be continued to temperatures well below TN. 相似文献
Magnetic susceptibility, specific heat and 133Cs magnetic resonance measurements in a single crystal of CsNiBr3 are reported. The data reveal two magnetic transitions separating the paramagnetic phase from the antiferromagnetic ground state. At the higher transition temperature TN2 = (14.25 ± 0.05)K a net magnetic moment is observed only along the hexagonal c-axis, while only below the lower transition temperature TN1 = (11.75 ± 0.05)K a perpendicular component of the magnetic moment appears also. Above TN2 CsNiBr3 can be described as a one-dimensional antiferromagnet with intrachain exchange interaction and single-ion anisotropy constant . Below TN1, the data are consistent with the non-colinear triangular structure of the Ni2+ moments proposed previously for the isomorphic crystal CsNiCl3. A reduced value of the zero-temperature susceptibility over the classical value is found and atrributed to the zero point deviations. 相似文献
Expressing the residual resistivity ?0 as a force-force correlation, a first-principles basis is afforded for the low temperature expansion of the electrical resistivity ? as
(I)
where λ = const T-2 is the non-resistive mean free path arising from electron-electron scattering. λ1 is found to reflect directly long-range correlations in the electronic motions via the off-diagonal behaviour of the local density of states at the Fermi energy. 相似文献
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
A new modification of molecular beam relaxation spectrometry (MBRS) is described: the temperature jump method for studying catalytic surface processes on metal foils. The temperature of the catalyst foil is maintained by direct ohmic heating; a constant particle beam is directed towards the catalyst surface. A jump of the surface temperature caused by a high current pulse generates a response of the fluxes of desorption. The decay of the desorption intensity after the temperature jump contains the relaxation times of the elementary steps involved. The mathematical treatments of unimolecular and bimolecular surface reactions, of sequences of two and three unimolecular steps and of a sequential reaction accompanied by the redesorption of the reactant are given. The application of the new method is shown by a study of the catalytic decomposition of CH3)OH on polycrystalline Ni: CO and H2 are the sole reaction products. The limit of the catalytic activity — apart from the low sticking probability of the reactant — must be seen in the abstraction of the first methyl hydrogen from the transient methoxy species. In the temperature range between 320 and 550 K the reaction mechanism can be described as follows: Rate constants in dependence from surface temperature T are: k1 = 4.2 × 104 exp s?1; k3 = 2.4 × 109 exp s?1; k4 = 1.2 × 1013 exp s?1; η = 0.2. Typical surface residence times of the intermediates are: 110 ? τ1 ? 15 ms at 320 ? T ? 450 K; 210 ? τ3 ? 6 ms at 450 ? T ? 550 K; 98 ? τ4 ? 6 ms at 450 ? T ? 500 K. 相似文献
The parallel magnetic susceptibility χ of a uniaxial ferromagnet ErCl3·6H2O has been measured between 0.3 and 4.2K and specially near Tc = 0.353 K. The predominant contribution to the Curie-Weiss temperature is due to the dipolar interactions. χ is proportional to ??γ with in the range 10?3 < ? < 5 × 10?2. The γ value, γ = 1.01 ±0.03 is consistent with the theoretical prediction for a uniaxial dipolar ferromagnet. 相似文献
Optical measurements on crystals in the series SnSxSe2?x for 0 ? x ? 2, have yielded information on the changes in the ordinary refractive index and the energy gap in the temperature range 125–425 K. The coefficient has values +40 to +160 × 10?6K?1 and this confirms that covalent bonding predominantly exists in these materials. The coefficient remains fairly consistent for all values of x with an average value of -8.0×10-4eV K-1. 相似文献
The diffusion constants for C and O adsorbates on Pt(111) surfaces have been calculated with Monte-Carlo/Molecular Dynamics techniques. The diffusion constants are determined to be DC(T)=(3.4 × 10?3e)cm2s?1 for carbon and DO(T) = (1.5×10?3 e) cm2 s?1 for oxygen. Using a recently developed diffusion model for surface recombination kinetics an approximate upper bound to the recombination rate constant of C and O on Pt(111) to produce CO(g) is found to be (9.4×10?3 e) cm2 s?1. 相似文献
The spontaneous magnetization of the sublattice vs temperature in the antiferromagnetic NiO was measured by the neutron diffraction method. Temperature changes of the Bragg peaks (111), (222), (333) and (444) with the wavelengths of neutrons , , and , respectively were simultaneously investigated by the neutron time-of-flight spectrometer. On the basis of these measurements, the transition temperature from the antiferromagnetic into the paramagnetic phase was determined, TN = (523 ± 1)°K. The temperature function of the (111) magnetic peak intensity has been accepted to be I ~ (TN?T)2β. According to the present measurements the critical point exponent is 0.33 ± 0.020.04. 相似文献
Giant quantum attenuation of longitudinal sound waves in Bi has been measured at temperatures down to 8 mK for the case that the electron (n = 0, s = + 1) and hole (n = 1, s = ? 1) Landau levels cross simultaneously Fermi level at a field of about 90 kOe. The temperature and frequency dependences of the peak attenuation due to these two levels are expressed by αp ∝ T-μων with and at T > 1 K. When T ? 1 K the value of μ decreases by decreasing temperature and below 0.1 K, αp takes almost constant value. At T ? 0.5 K, ν becomes larger than 1 and maximum value of ν observed is 2 at T ~ 0.05 K. These features of the attenuation peak at very low temperatures are consistent with what are expected in the fluctuation region of the gas-liquid type transition of the electron-hole system. 相似文献
It is shown that the thermal fluctuations depin the charge density wave of the Peierls Fröhlich state pinned by impurities at absolute zero temperature. The critical temperature, Td, of this depinning is estimated as where m1 and γ0 are the mass of the collective mode and the pinning frequency at T = 0. 相似文献
The effect of fluctuating Cooper pairs on the diamagnetic susceptibility of dirty superconducting thin films is investigated, for temperature T < Tc. The susceptibility decreases with the decrease in temperature, approaching at T = 0°K and remains finite at T = Tc. 相似文献