摘要:

Fields and currents induced by vortex structures in a Josephson junction in a thin superconducting film are considered. Simple asymptotic regularities describing fields and currents induced by solitary Abrikosov–Josephson vortices and periodic chains of such vortices are obtained. These regularities are applied to some nonlinear small-scale states. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593415

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Temperature dependence of the amplitude and ballistic velocity of a high-frequency signal (quasiwave) in a superconductor, associated with the energy dependence of the velocity of electron excitations, is studied theoretically. The spatial distribution of the quasiwave field and the transformation coefficient are calculated for quasiwave excitation by an electromagnetic wave as well as by longitudinal or transverse elastic deformation. The obtained results are in accord with the data on electron sound velocity measurements in the superconducting states of Ga, Mo, and Al. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593416

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The equation for hypervortex in a slightly granular superconductor is obtained, and the vortex lattice is numerically simulated. The dissipation associated with the formation, collapse, and movement of hypervortices is considered. The equations describing the dynamics of magnetic field distribution, nonlinear susceptibility, and current–voltage characteristics in the resistive state are obtained. The numerically simulated equations give results that are in good agreement with those obtained experimentally. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593417

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A microscopic approach to the description of multisublattice magnets with strong exchange interaction is proposed. Low-frequency dynamics of such magnets is characterized by the appearance of an additional dynamical variable, i.e., the orthogonal matrix of rotation, which corresponds to the total breaking of spin invariance [brokenSO(3)symmetry]. The structure of the source that breaks the symmetry of the equilibrium Gibbs distribution is established. The quasiaverage representation is generalized to weakly anisotropic, locally equilibrium states. The thermodynamics of such states is constructed. The method of reduced description is formulated and in its framework the hydrodynamic equations for the density of total spin and the matrix of rotation are obtained. The spectra of spin waves are found and the number of Goldstone and activation modes is determined. Two-sublattice ferrimagnet is considered as a special case of the magnet with brokenSO(3)symmetry, which corresponds to the special dependence of thermodynamic functions from the matrix of rotation. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593418

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The spectral structure for an openX–Ychain is determined rigorously, and one-fermion states are classified for all values of anisotropy and transverse field. Quasidegeneracy is interpreted as well as the general nature of ordering in a certain class of systems with a locally nondegenerate ground state. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593419

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Dynamic susceptibility of the one-dimensional spin-1/2transverse Ising model is obtained by using the numerical approach suggested earlier [Ferroelectrics153, 55 (1996)]. The dependence of the susceptibility frequency shapes on the value of the transverse field at various temperatures is discussed. The way in which the frequency shape rebuilds as the transverse field increases is illustrated. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593420

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Using57Coemission Mo¨ssbauer technique, we present clear evidence that in Ca-doped manganite, the magnetic and paramagnetic phases coexist belowTC,with the abundance of the latter increasing with temperature. In contrast with the regular ferromagnetic materials, the variation of the hyperfine internal magnetic fieldHintwith temperature deviates considerably from the Brillouin relation, and exhibits an abrupt drop atTC.These features characterize the magnetic transition as a first-order transition. The non-Brillouin behavior ofHint(T)and the temperature dependence of the shape of the magnetically split sextet indicate the presence of spin fluctuations in this material well belowTC.©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593421

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We follow the step-by-step progression of events while approaching the Curie temperatureTCfrom below using57Cosubstituent as a microprobe in an emission Mo¨ssbauer study combined with resistivity measurements. In the temperature range0.33<T/TC⩽1,the material consists of a mixture of ferromagnetic and paramagnetic regions within the same matrix. An increase of the amount of paramagnetic fraction is accompanied by a decrease in electron delocalization in the ferromagnetic regions. AtT⩾TC,the electrons are localized to neighboringMn4+/Mn3+pairs only, in about 46&percent; of the paramagnetic species. The strength with which Mn atoms are bound to the neighbors also decreases progressively and rather steeply in the range0.65⩽T/TC=1.Zero field resistivity,&rgr;0,follows linearly with the amount of the paramagnetic phase in the range0.65⩽T/TC⩽1and still shows metal-like behavior up toT/TC=1.03.©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593422

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have made an electron-microscopy study of nanoholes in membranes in successive stages of metal deposition using two different techniques: physical vapor deposition (PVD) and chemical vapor deposition (CVD). One-sided PVD (thermal evaporation) of gold and silver was used, as is relevant for heterocontacts. The key results in this case are: 1) the holes are not filled during deposition and 2) closing of the holes is accomplished by lateral growth of the film on the membrane. In the case of CVD of tungsten we found that nanoholes in membranes are filled at the beginning of the deposition, and that the process is capable of filling holes as small as 10 nm. Fabricated devices (&agr;-tungsten) show good quality point-contact spectra which are characteristic of ballistic transport through the constriction. A very interesting stepwise current increase was observed for one amorphous tungsten point contact. ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593430

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The influence of intercalated hydrogen concentration on the physical properties ofNbSe3is investigated. The mass-spectrometric analysis reveals a nonlinear dependence of hydrogen extraction from the crystal structure on the saturated pressure. Resistive measurements make it possible to study the concentration dependence of the temperatureTCDWcorresponding to a phase transition accompanied with the formation of a charge density wave (CDW) and temperature dependence of CDW pinning threshold fields. A metal-semiconductor phase transition is observed for certain concentrations of intercalated hydrogen. All the measurements are made in the temperature range of the first CDW transition (90–300 K). ©1997 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593423

出版商:AIP    

年代:1997

数据来源: AIP