摘要:

The propagation of fourth sound waves in a solution of two superfluid liquids3He–4Heis considered by taking into account the effect of reciprocal drag of superfluid motions. It is shown that the inclusion of the drag effect leads to a change in the ratio of intensities of second and first fourth sound waves. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593525

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The equations describing the propagation of acoustic waves in relativistic superfluid two-condensate systems are derived and solved. It is shown that the presence of an additional acoustic mode and two types of waves of fourth sound is a peculiarity of the system under investigation. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593526

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The molecular dynamics method is applied to theLa2−xSrxCuO4system to prove that canonicity conditions are violated in the case of a large contribution of anharmonism. This can lead to the formation of “hot” regions∼0.5 nmin the vicinity of Sr impurity atoms with an average kinetic energy two or three orders of magnitude higher than in the matrix even at low temperatures. The matrix is “effectively” cooled and can basically carry superconducting current due to percolation for any electron pairing mechanism. The velocity distribution is described by not one but at least two Maxwell functions. The fcc lattice of Ni near the phase-transition point also acquires “hot” spots which are not, however, localized in space, but migrate (with a lifetime∼10−12 s)and have a much smaller difference in kinetic energies (by a factor of 1.5–2.0). At low temperatures, canonicity conditions are always satisfied. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593527

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The dynamics of small-angle domain walls existing in an easy-axis ferromagnet in the vicinity of spin-reorientation phase transition in an external in-plane magnetic field is studied. The dependence of the drift velocity on the amplitude, frequency, and polarization of the oscillating field is obtained. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593528

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Second-order nuclear magnetic relaxation associated with electric quadrupole interaction between paramagnetic centers and two-level systems is studied. First- and second-order relaxation times are compared. It is shown that second-order relaxation prevails in relatively low magnetic fields. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593529

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Thermodynamics of glass-forming liquids and glasses is considered taking into account the contribution of heterophase fluctuations to the free energy. The role of heterophase fluctuations in liquids and glasses is played by nuclei of noncrystalline solids and nuclei of the liquid phase respectively. Crystalline solid state is not considered. Free energy is described on the bases of the droplet model and the model of mixed state. It is shown that three regions of stability of different structural states of the system exist on the(P,T)plane. Two of them are stability regions for droplet structural states, while the mixed state is stable in the third region in which heterophase fluctuations have the form of isolated drops. In this state, two infinite percolating clusters (liquid and noncrystalline solid) coexist. The width of the temperature interval[Tt1,Tt2]in which the mixed state is stable increases with configuration entropy (complexity) of the noncrystalline solid fraction. In the approach used, weak first-order phase transitions are observed atT=Tt1andT=Tt2.It is shown that first- and second-order phase transitions are possible in the mixed state. The criteria for the existence of these phase transitions are obtained. Equations of state and expressions for thermodynamic parameters (entropy, heat capacity, compressibility, and thermal expansion coefficient) are derived for the droplet and mixed states. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593530

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Temperature dependences of resistivity and current-voltage characteristics ofNbSe3single crystals intercalated with hydrogen are investigated in the temperature range 90–300 K in the normal state and in a state with a charge density wave near the first phase transition at 145 K. A state with nonlinear conductivity atT>145 K,IVC with a negative differential resistance, and low-frequency voltage oscillations in the state with the CDW are discovered. The results are interpreted on the basis of concepts of redistribution of intercalated hydrogen under the action of temperature diffusion and electric field during the propagation of a charge density wave. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593531

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Point-contact spectra of organic conductors[(C2H5)4N]0.5[Ni(dmit)2]and(BEDT-TTF)2I3have been measured. The plots of point-contact functions of the electron–phonon interaction in these compounds have been constructed, and mean and root-mean-square values of frequency have been obtained. The relation between the intensity of the electron-vibrational interaction and conducting properties of the materials under investigation have been obtained. A correlation is observed between the intensity of these processes and the superconducting transition temperature. The criterion for the synthesis of new organic superconductors is discussed. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593532

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The behavior of nitrogen, hydrogen, and deuterium atoms trapped from the gaseous phase and matrix-isolated in solid molecular hydrogen are studied by the EPR method. It is established that all these atoms are localized in the substitutional position of the matrix crystal lattice. The linewidths in the EPR spectrum of nitrogen are found to be one fourth of the linewidths recorded by most authors. It is shown that a version of theoretical calculation gives a linewidth matching with the experimental value. It is proposed that two different types of matrix surroundings are possible for a nitrogen atom trapped in the substitutional position, one of which corresponding to the undistorted crystal lattice ofN2.The EPR line broadening under the action of zero-point atomic vibrations is observed for hydrogen and deuterium atoms. The magnitude and temperature dependence of the spin-lattice relaxation time for N, H, and D atoms in the solidN2matrix are obtained experimentally. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593533

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A peak of acoustic emission (AE) is observed experimentally at the superconducting transition temperature in samples of the superconducting ceramicsTl2Ba2CuO6+x.AE signals have been recorded by a piezoelectric transducer with the resonant frequency 1 MHz in the temperature range 80–300 K. Relaxation anomalies are attributed to a change in the charge state of linear defects and variations of the parameters of the cuprate layer in the samples. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593534

出版商:AIP    

年代:1998

数据来源: AIP