摘要:

AbstractThe structure and structural changes of an Al78Cu22(at%) alloy film produced by coevaporation onto a cooled substrate have been investigated with transmission electron microscopy. A series of metastable phase transitions were observed during the crystallization from the as‐deposited amorphous phase to the final equilibrium state. The deposit structure at room temperature consists of a mixture of fine grained α' crystallites (fcc, α = 4.81 Å) with an amorphous phase, and some welldefined crystals with an fcc lattice (a= 7.18 Å, namely α1). The subsequent annealing led to the grown crystals transforming to an ordered α′ phase. It is argued that the development of such a transition is the result of a gradual atomic rearrangement – first topologically then a chemically predominant disorder‐ord

ISSN:0003-3804    

DOI:10.1002/andp.19935050302

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe two‐rotor model0 with the Feshbach projection operator method is applied for investigating the properties of the positive parity low‐lying collective states in the rare earth nuclei. The calculations of the energy spectra, E2‐transition probability and magnetic properties of the states of β‐ and γ‐bands are carried out for the isotopes164, 166, 168Er. The B(M1) values from 1+states to the ground band ar

ISSN:0003-3804    

DOI:10.1002/andp.19935050303

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe astrophysicalS‐factor for the reaction7Be(p, γ)8B up to an energy of 2 MeV (c.m.) and the capture cross section of7Li(n,γ)8Li up to 1 MeV (c.m.) are calculated using the Direct Capture model (DC). Both calculations are in good agreement with experimental d

ISSN:0003-3804    

DOI:10.1002/andp.19935050304

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractBy expressing the free energy as an appropriate temperature integration over the square of the BCS energy gap function and by substituting simple but accurate analytic expressions for the latter, corresponding expressions are obtained for the specific heat in the superconducting state. In the upper portion of the temperature range, the ratio of the specific heats in the superconducting and normal states is 2.43 (1 + 0.936 int), to better than one per cent accuracy, wheretis the reduced temperature. Thus, the semilog plot of temperature versus the ratio of specific heat to temperature is a straight line over a large portion of one decade of specific heat. Corresponding expressions of similar simplicity and accuracy are obtained for the middle and low temperature ranges.

ISSN:0003-3804    

DOI:10.1002/andp.19935050305

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractThe oxygen isotope effect in high‐TCsuperconductors has been investigated on the basis of a two‐band model where superconducting phase transition is induced by interband (mainly Coulombic) interaction. The isotope shift ofTCappears due to the dependence of averaged interband electronphonon coupling constant on oxygen mass. This coupling has a repulsive nature and gives a relatively small contribution to the total interaction inducing superconductivity. The calculated isotope effect exponent depending on the carrier concentration has been compared with the experimental one as a function ofxfor La2‐xSr

ISSN:0003-3804    

DOI:10.1002/andp.19935050306

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractWe discuss the questions related to modifications of the orthorhombic phase of YBCO. A general approach of statistical mechanics allows to determine numerically such quantities as the paramagnetic Curie constant, concentration of holes doped into Cu(2) planes from chain fragments, the fractions of copper ions in differently coordinated positions. Where the experimental information is available, we discuss a correspondence between our theoretical results end experimental ones.

ISSN:0003-3804    

DOI:10.1002/andp.19935050307

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractMany stationary forms of self‐localized modes exist in a simple square and hexagonal lattice. They consist of a certain number of an elementary self‐localized anharmonic mode (SLAM). This has several shapes depending on the uniform power of the nearest‐neighbour interaction. By comparing SLAMs of the same vibrational frequency a binding energy can be derived for each stationary aggregated SLAM. Also infinite chains and whole lattices of elementary SLAMs are obtained. They have to be distinguished from standing waves of single‐anharmonic

ISSN:0003-3804    

DOI:10.1002/andp.19935050308

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

摘要:

AbstractWe investigate the spin dynamics of the classical two‐dimensional easy‐plane Heisenberg antiferromagnet with an additional Dzyaloshinsky interaction, which serves as a simple model for Langmuir‐Blodgett films of Mn (C18H35O2)2. By mapping the system onto a pure easy‐plane model we discuss the corresponding spin wave and vortex dynamics. The additional Dzyaloshinsky interaction forces all spins to cant in a certain direction, which is the same for neighboring spins on different sublattices. This canting causes the presence of a second spin wave peak in the dynamical in‐plane correlation function below the Kosterlitz‐Thouless transition temperatureTKTand a second vortex central peak aboveTKT. Using a vortex gas approach we explicitly calculate the contribution of the free vortices to several dynamical correlation functions. These results are compared to a combined Monte Carlo‐Molecular Dynamics simulation on square lattices with different sizes. We also discuss the relevance of this simple model for describing the spin dynamics of M

ISSN:0003-3804    

DOI:10.1002/andp.19935050309

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY

ISSN:0003-3804    

DOI:10.1002/andp.19935050301

出版商:WILEY‐VCH Verlag    

年代:1993

数据来源: WILEY