摘要:

It is shown on the basis of the solution of the kinetic equation for the gas of impurity excitations of superfluid mixtures3He–4Hethat the relaxation of concentration and temperature occurs due to two modes (acoustic and dissipative). The parameters characterizing these modes are determined. The obtained results show that the relaxation of concentration and temperature of impuritons is completely determined by the thermal conductivity of the mixture and by the acoustic mode (second sound). ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593444

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Frequency spectrum of small-amplitude oscillations of magnetization against the background of coherently precessing (phase-correlated) spin modes in superfluid3Heplaced in a strong magnetic field depends on the magnitude of spin polarizationSand spin-orbit structure of dynamical ordered states. Spectrum of these oscillations is calculated for unconventional precessing modes in3He-Bcharacterized byS=S0/2,whereS0is the value ofSat equilibrium. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593432

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The temperature and size dependences of critical current of three bismuth-based and one yttrium-based ceramic samples of rectangular cross sections in zero magnetic field are studied by a contactless method. It is shown that the critical current in ceramic HTS can be presented as the product of temperature- and size-dependent factors. The temperature-dependent factor describes the individual properties of Josephson net for each sample, while the size-dependent factor is a universal homogeneous function whose index is independent of the ratio of the sides of the cross section, temperature, and individual properties of the HTS sample. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593433

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

It is shown that the phase diagram of a2Dmetal with a varying charge carrier density consists of normal phase regions in which the modulus of the order parameter is zero, the so-called anomalously normal phase in which it differs from zero but has a random phase, and the Berezinskii–Kosterlitz–Thouless phase. The characteristic temperatures of transitions between these phases are determined as well as the behavior of the chemical potential as a function of the fermion density and temperature. An attempt is made to compare qualitatively the obtained phase diagram with the observed peculiarities in the behavior of underdoped high-Tcsuperconducting compounds above their critical temperature. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593434

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The possibility of studying the anisotropy of lower critical fields in HTS materials during the measurements of critical currents of textured samples subjected to the action of magnetic fields applied in three different directions is explored in the theory of magnetic properties of anisotropic superconductors. The critical fieldsHc1abandHc1cof the high-TcmaterialsYBa2Cu3O7−&dgr;andDyBa2Cu3O7−&dgr;are determined atT=77.3 K.It is found that the dependencesHc1ab(mc/mab)andHc1c(mc/mab)are universal for all the investigated samples. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593476

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A nonlinear evolution system of hydrodynamic-type equations describing a three-dimensional multisublattice magnet is investigated. Explicit form of the energy density function for magnetic systems that have an invariant energy density relative to right and left spin rotations is obtained. For quadratic-biquadratic dependence of the energy density (in terms of Cartan’s invariant functions), exact solutions are obtained in the one-dimensional case for spin density in the form of stationary profile waves. Solutions for magnon fields that induce such waves are also obtained. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593435

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Magnetic and galvanomagnetic properties of ordering alloysPd2AuFeare studied in fieldsH⩽12 MA/matT=4.2 K.It is shown that the disappearance of spontaneous magnetization in the region of ferromagnetic–antiferromagnetic phase transition which occurs as a result of atomic ordering of thePd2AuFealloys is accompanied by peaks of paraprocess susceptibility and of the anomalous positive Hall effect. The sign of the normal Hall effect is reversed in this case. It is shown that the peculiarities of galvanomagnetic properties are associated with the rearrangement of the electronic band structure during ordering of the alloys. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593436

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Magnetoresistive properties of thinLa0.5Pb0.2Ca0.2Y0.1MnO3−&dgr;films obtained by magnetron sputtering technique are studied. A giant decrease in resistance (up to98&percent;)in magnetic fieldsH=10 Tis observed at a temperature of 175 K. The physical factors responsible for the effect of composition and preparation technique on their magnetotransport properties are discussed. The mechanisms and empirical relations describing the temperature and field dependences of the resistive properties of films are also discussed. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593437

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The spin structure of magnetic disclination, viz., spin inhomogeneity manifested in antiferromagnets in the presence of a dislocation, is analyzed. The analysis is carried out on the basis of the discrete model as well as in the specially constructed generalized continual theory based on the local introduction of the antiferromagnetism vectorland taking into account the possibility of a change in the length of this vector. In the solution without singularities constructed for disclination, the modulus of the antiferromagnetism vector vanishes at the center of the disclination. In the discrete model, the disclination energy depends significantly on the arrangement of spins near the core and on the type of their interaction. With the proposed model of spin arrangement, the results of numerical analysis based on the discrete and continual models are in good agreement. It is shown that planar disclinations are stable to the emergence of spins from the easy plane. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593438

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The change in the lattice parameter&Dgr;a/aof monocrystallineC60films of thickness less than 10 nm is determined by the transmission high-energy electron diffraction method. In the temperature range 90–260 K, the value of&Dgr;a/aincreases with decreasing film thickness. The results are used for calculating the coefficients&agr;fand&agr;sof linear thermal expansion of the films and of the surface atomic layer. The value of&agr;salong the (111) plane is equal to(55±15)×10−6 K−1.©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593442

出版商:AIP    

年代:1997

数据来源: AIP