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101.
The specific heat of Fermi–Pasta–Ulam systems has until now been estimated through the energy fluctuations of a suitable subsystem, and opposite answers were apparently provided concerning its possible vanishing for vanishing temperatures. In the present paper a more realistic numerical implementation of the specific heat measurement is discussed, which mimics the interaction of the FPU system with a calorimeter. It is found that there exists a freezing critical temperature below which the relaxation times to equilibrium between FPU system and calorimeter become relevant, so that the system presents aging and hysteresis features very similar to those familiar in glasses and spin glasses. In particular, in the framework of such a point of view involving finite long times, the specific heat appears to vanish for vanishing temperatures. 相似文献
102.
C. Djurberg K. Jonason P. Nordblad 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(1):15-21
Experiments on the temperature and time dependence of the response function and the field cooled magnetisation of a Cu(Mn)
spin glass at temperatures below the zero field spin glass temperature are used to explore the non-equilibrium nature of the
underlying spin configuration. The results imply that a certain spin configuration is imprinted on the system as the temperature
is decreased at a constant cooling rate. The cooling rate governs the magnitude of the FC magnetisation ((H,T)). Any intermittent halt at a constant temperature, , imprints an extended spin configuration, a process that is reflected e.g. in a downward relaxation of . On continued cooling at the same rate, the magnitude of (T) remains at a lower level than that of a continuous cooling curve. These results are put into the context of the corresponding
behaviour of the response function as observed in measurements of the relaxation of the zero field cooled magnetisation.
Received 27 October 1998 and Received in final form 30 November 1998 相似文献
103.
Multi-layered thin films, which consisted of metallic silver, GeSe3 glass, and silver oxyhalide superionic conductor glass were prepared. Photo- and electrochemical reaction of metallic silver with the chalcogenide glass layer was studied by optical absorbance and cyclic-voltammetry. Photo-doping of silver through the superionic glass layer was observed using evaporated AgI---Ag2MoO4 film and it was partly undoped by electrochemical treatment. However, no photo-doping was observed for the cell consisting of a AgI---AgPO3 dip-coated layer. The doped silver was dissolved into the GeSe3 layer during the photo-doping process. However, it formed another intermediate compound layer (probably silver selenide) during the electrodoping process. 相似文献
104.
The effect of pressure on the conductivity of fast ion conducting AgI-Ag2O-MoO3 glasses has been investigated down to 150 K. The observed variation of conductivities appears to support the application
of cluster model to the ionic glasses.
Contribution No. 258 from the Solid State and Structural Chemistry Unit. 相似文献
105.
The Ising model with competing interactions is studied in a mean field effective medium approach. The phase diagram of such
model alloys is studied. We conclude that for all ratios of the competing interaction moments, a spin glass phase always exists
at low temperatures for certain concentration regimes. 相似文献
106.
The IR spectra of glasses of the ZnO—SrO—B2O3 system with constant additions of PbO, Al2O3, and Li2O (20 mol. % in sum) were studied. It is established that on replacement of B2O3 by ZnO, the structure of the glasses is characterized by the presence of groupings with the bridge bonds BIII— O—BIII, BIII—O—BIV, BIV—O—BIV and end groups BIII— O−; ZnO practically exerts no influence on the coordination transition [BO3] → [BO4]. At a high content of ZnO, zinc ions are present in both a six-and a four-coordinated state.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 778–781, November–December, 2005. 相似文献
107.
Jose G Jose G Thomas V Joseph C Ittyachen MA Unnikrishnan NV 《Journal of fluorescence》2004,14(6):733-738
Silica glass samples containing CdSe/Eu3+ ions were prepared by sol-gel route. Size distribution and optical band gap of the nanoparticles were calculated from absorption spectrum. It is observed that the presence of CdSe nanocrystallites enhances the fluorescence of europium in silica glass. The phonon sideband spectrum associated with the excitation transition 7F0-5D2 is used to analyze the electron-phonon coupling and nonradiative deexcitiation of the rare earth ions in the glass host, The observed fluorescence enhancement is discussed on the basis of phonon assisted energy transfer from electron-hole recombination of the CdSe nanocrystallites to the rare earth ion and multiphonon relaxation. 相似文献
108.
Peter?EichelsbacherEmail author Matthias?L?we 《Probability Theory and Related Fields》2004,130(4):441-472
We derive moderate deviation principles for the overlap parameter in the Hopfield model of spin glasses and neural networks. If the inverse temperature is different from the critical inverse temperature c=1 and the number of patterns M(N) satisfies M(N)/N 0, the overlap parameter multiplied by N, 1/2 < < 1, obeys a moderate deviation principle with speed N1–2 and a quadratic rate function (i.e. the Gaussian limit for = 1/2 remains visible on the moderate deviation scale). At the critical temperature we need to multiply the overlap parameter by N, 1/4 < < 1. If then M(N) satisfies (M(N)6 log N M(N)2N4 log N)/N 0, the rescaled overlap parameter obeys a moderate deviation principle with speed N1–4 and a rate function that is basically a fourth power. The random term occurring in the Central Limit theorem for the overlap at c = 1 is no longer present on a moderate deviation scale. If the scaling is even closer to N1/4, e.g. if we multiply the overlap parameter by N1/4 log log N the moderate deviation principle breaks down. The case of variable temperature converging to one is also considered. If N converges to c fast enough, i.e. faster than the non-Gaussian rate function persists, whereas for N converging to one slower than the moderate deviations principle is given by the Gaussian rate. At the borderline the moderate deviation rate function is the one at criticality plus an additional Gaussian term.Research supported by the Volkswagen-Stiftung (RiP-program at Oberwolfach, Germany).Mathematics Subject Classification (2000): 60F10 (primary), 60K35, 82B44, 82D30 (secondary) 相似文献
109.
J.A. Hodges P. Bonville A. Forget J.P. Sanchez P. Vulliet M. Rams K. Królas 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(2):173-181
Using 170Yb and 155Gd M?ssbauer measurements down to ∼ 0.03 K, we have examined the semiconducting pyrochlore Yb2Mo2O7 where the Mo intra-sublattice interaction is anti-ferromagnetic and the metallic pyrochlore Gd2Mo2O7 where this interaction is ferromagnetic. Additional information was obtained from susceptibility, magnetisation and 172Yb perturbed angular correlation measurements. The microscopic measurements evidence lattice disorder which is important in
Yb2Mo2O7 and modest in Gd2Mo2O7. Magnetic irreversibilities occur at 17 K in Yb2Mo2O7 and at 75 K in Gd2Mo2O7 and below these temperatures the rare earths carry magnetic moments which are induced through couplings with the Mo sublattice.
In Gd2Mo2O7, we observe the steady state Gd hyperfine populations at 0.027 K are out of thermal equilibrium, indicating that Gd and Mo
spin fluctuations persist at very low temperatures. Frustration is thus operative in this essentially isotropic pyrochlore
where the dominant Mo intra-sublattice interaction is ferromagnetic.
Received 13 January 2003 Published online 4 June 2003
RID="a"
ID="a"e-mail: hodges@drecam.saclay.cea.fr 相似文献
110.
Physical ageing effects caused by prolonged natural storage are recorded for binary AsxSe1−x glasses with 0.2x<0.4. Their origin is associated with pure “shrinkage” of under-constrained glass networks. It is shown that only stoichiometric As2Se3 composition, which network is formed by a so-called self-organized phase, possesses the ideal non-ageing ability. 相似文献