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1
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A Simple Model for the Surface Phenomena

100%
Wojtczak L.
Acta Physica Polonica A
|
1993
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vol. 83
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issue 5
685-699
EN
The simplicity of the present model consists in the construction of the Hamiltonian based on the models of quasi-harmonic oscillators coupled to quasi-free electrons with the effective parameters which are estimated by means of the pseudoharmonic approach and coherent potential approximation, respectively. The geometry of a sample is determined by the topological disorder at the surface reflecting the surface roughness. The model is discussed in connection with the friction related to the melting and pre-melting phenomena. The backscattering of electrons seems to be a testing tool useful not only for decorated surfaces but also for quasi-liquid layers.
2
Content available remote

The Magnetic Equation of State and Transport Properties in Reduced Dimensions

63%
Warda K., Wojtczak L.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 4
878-880
EN
Basing our considerations on magnetic equation of state applied to the description of magnetic systems of confined geometry we developed the model of calculations of the electrical resistivity for metallic multilayers. It was shown that in the transport of charge in ferromagnetic material d-electrons play an important role. The key parameters in the presented model are: the width of the electron energy band and the shift of the energy level for two spin orientations as well as the Fermi energy and size of the sample (the thickness of magnetic and nonmagnetic layers and the total number of layers). The presented results of calculations for temperature dependence of magnetoresistance are in qualitative agreement with the available experimental data. The model calculations introduced in this paper can be applied to current-in-plane geometry as well as to current-perpendicular-to-plane geometry. The calculations are valid within the limitations of the resistor network model.
3
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Dependence of Work Function on Surface Magnetization

63%
Baczyński J., Wojtczak L.
Acta Physica Polonica A
|
1991
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vol. 80
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issue 5
707-716
EN
It is shown theoretically that, in contradiction to massive specimens, the work function of ferromagnetic thin films does not depend linearly on the square of magnetization as a consequence of the inhomogeneous magnetization distribution. This theoretical conclusion is confirmed by experimental investigations of gadolinium films as well as interpretation of the results reported for nickel samples.
4
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Pressure Influence on the Curie Temperature

51%
Rutkowski J., Wojtczak L., Zajac Š.
|
|
issue 5
745-746
EN
The pressure dependence of the ferromagnetic-paramagnetic phase transition temperature T_{C} (p) is of high interest due to its direct technological implications. The theoretical investigations of the Curie temperature T_{C} (p) considered in the ferromagnetic crystals have been studied employing various methods of calculations. The present paper is devoted to its description by means of the pseudoharmonic approximation approach.
5
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Two-Site Correlations in a Surface Layer Adsorbed on the Crystal

45%
Wojtczak L., Zasada I., Le Bossé J., Lopez J., Rousseau J.
Acta Physica Polonica A
|
1991
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vol. 80
|
issue 5
631-648
EN
The incohorent scattering of electrons by layer adsorbed at a single crystal surface is determined by the Fourier transform of correlation functions of elements forming this layer. The model of the description of atoms or molecules adsorbed on the surface is formulated by the occupation operators which are represented by the pseudospin operators. The calculations of the correlation functions are performed by means of methods which consider a given pair of elements embedded in the effective field of remaining elements of the system while the interaction between the elements of the pair are taken in its exact form. Two approaches are presented here, i.e. the cumulant average and constant coupling approximations, and the case of binary chemisorption is considered in detail. The problem of the correlation symmetry is also discussed.
6
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Topological Correlations in a Layer Adsorbed on a Crystal Surface

45%
Wojtczak L., Zasada I., Bosse Le J. C., Lopez J., Rousseau J., Institute of Physics U. o. Ł., Laboratoire de Physique des Interfaces B.
Acta Physicae Superficierum
|
1990
|
vol. 1
EN
The incoherent scattering of electrons by a layer adsorbed at a single crystal surface is determined by the topological correlations of elements forming the adsorbed layer. The model for the description of atoms or molecules adsorbed on the surface is formulated in terms of occupation operators which are expressed in terms of pseudospin operators with a given spin value. The correlations can be determined by the fluctuation dissipation theorem in connection with the susceptibility or given directly by means of the Green functions properly chosen. An example of the topological or chemical disorder of two components is considered in detail. The calculations of the topological correlations allow us to find the incoherent scattering amplitude as a function of the surface coverage which can be experimentally detected.
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