摘要:

A theoretic analysis of magnon-induced damping &Ggr; of quasiparticle states in the normal phase of doped copper-oxide high-Tcmaterials is developed, based on a microscopic model which accounts for the specific2Dstructure of their electron and magnon spectra. Among the obtained energy and temperature dependencies of &Ggr; in different regimes, the most peculiar is the anomalously early onset of linear temperature dependence&Ggr;∝Twith a doping-independent coefficient. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593623

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The limitation of critical current in highTcsuperconducting YBCO thin films has a varied nature according to the quality of YBCO films. Our results showed that in strips from granular films the weak links of superconductor–normal metal–superconductor and superconductor–constriction–superconductor types were responsible for critical current limitation. In the YBCO strips with improved (preferential) crystallographic orientation a flux-creep critical current limitation was found and in the highly oriented YBCO strips the Ginzburg–Landau depairing mechanism approximated the critical current limitation for temperature close toTc.©1998 American Institute of Physics. 

ISSN:1063-777X    

DOI:10.1063/1.593624

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Anomalies in ohmic losses in HTSC ceramics are considered in the low- and radio-frequency ranges. It is found experimentally that the width of theN–Stransition in the ceramics(YBa2Cu3O7+1&percent; 57Fe),SmBa2Cu3O7,andYBa2Cu3−xScxO7in a weak magnetic field (up to 50 Oe) becomes smaller in the frequency interval betweenfcandfFat which the resistance does not depend on temperature. It is shown that, for some types of HTSC and for different samples of the same type, the frequencyfcdoes not correlate with the superconducting transition temperatureTc.©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593625

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The behavior of uniaxial paramagnets in a tilted magnetic field is considered as a function of temperature. The structure of the energy spectrum as well as magnetization and susceptibility components are determined. Exact formulas for the spinS=1/2are obtained. Thermodynamic parameters of the system are studied for arbitrary values ofSin an easy-axis and easy-plane cases in different approximations (weak and strong magnetic fields, low and ultralow temperatures, etc.). It is shown that in the easy-plane case, the transverse magnetization and longitudinal susceptibility as functions of magnetic field at low temperatures exhibit peculiarities in the form of a series of sharp spikes, while the longitudinal components of these quantities in the easy-axis case display only a single spike. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593626

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The spin dynamics of a domain wall is studied in an infinite ferromagnetic chain with an easy-axis anisotropy as well as in a chain of finite size. The dependence of the intrinsic mode frequency of the domain wall on the exchange interaction is studied for all admissible values of the latter. It is shown that this dependence is considerably modified in the region of transition of the domain wall from collinear structure to canted form. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593627

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Many-particle bound states in a Bose gas with a complex pair interaction between particles are considered. It is shown that the combination of attraction and repulsion between particles leads to the emergence of bound states with peculiar physical properties. In the limit of a large number of bound states in the Hartree approximation, these states are close in the structure and properties to exotic solitons (compactons and peakons) in classical systems with weak spatial dispersion. Examples of exotic solitons of various types in magnetically ordered media are considered. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593628

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Spin waves in a non-ferromagnetic electron liquid in a magnetic field are studied in the random phase approximation. The electron bound states in the field of impurity atoms are considered. It is shown that electron localization facilitates the propagation of spin waves. New branches of wave spectrum are found in the frequency region where propagation of Silin’s waves is not possible. The spectrum and damping decrement of waves are obtained. Intersection of the dispersion curve for a Silin wave with the resonance frequency of electron transitions between Landau levels and local levels results in a cross situation typical of coupled waves. The differential cross-section of magnetic scattering of neutrons by a two-dimensional electron liquid in a magnetic field is calculated. The energy spectrum of scattered neutrons contains additional peaks associated with one-particle excitations of localized electrons and spin waves. The positions and widths of these peaks provide information about the spectrum of electron impurity states as well as the spectrum and damping of spin waves. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593629

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The size-effect of Kondo-scattering in nanometer-sized metallic point contacts is measured with the simplified, mechanically-controlled break–junction technique for CuMn alloy of different Mn concentrations: 0.017; 0.035; and 0.18 (±0.017) at.&percent;. The results are compared with our previous publication on nominally 0.1 at. &percent; CuMn alloy.12The increase of width of the Kondo resonance and enhanced ratio of Kondo-peak intensity to electron–phonon scattering intensity is observed for contacts with sizes smaller than 10 nm. From the comparison of electron–phonon scattering intensity for the pressure-type contacts, which correspond to the clean orifice model, we conclude that the size effect is observed incleancontacts with the shape of achannel(nanowire). ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593630

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A simple theory that makes it possible to calculate the characteristics of metal–insulator–thin metal film tunnel junctions is developed. Along with the well-known oscillations in the voltage dependence&sgr;(V)of tunneling conductance due to commensurate states, it predicts a number of new effects. For example, even in the case of a symmetric tunnel junction formed by the identical materials with a rectangular potential barrier, the&sgr;(V)curve displays a noticeable asymmetry. The branch of the&sgr;(V)curve corresponding to tunneling to the thin-film electrode contains a structure consisting of conductance dips. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593631

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Tunneling experiments with Bi2223 reveal that a decrease in the carrier concentration shifts the boundary frequency&ohgr;0of the cuprate phonon spectrum towards higher frequencies from&ohgr;0=98 mV(Tc=113 K)to&ohgr;0=106 mV(Tc=107 K)with an insignificant suppression of the energy gap parameter &Dgr;. ©1998 American Institute of Physics.

ISSN:1063-777X    

DOI:10.1063/1.593618

出版商:AIP    

年代:1998

数据来源: AIP