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Thin S = 112 ferromagnetic film with exchange interaction enhanced near the film surface is considered in the Ising model. As a result the phase diagrams, the magnetization profiles, and magnetization curves for several particular cases are presented. A modified definition of the critical A , parameter for the thin film case is also proposed.Im Ising-Model1 wird eine ferromagnetische Schicht mit S = 112 und erhohter Austauschwechselwirkungin der Nahe der Schichtoberflache untersucht. Als Ergebnis werden Phasendiagramme, Magnetisierungsprofile und Magnetisierungskurven fur einige besondere Falle angegeben. Eine modifizierte Definition des kritischen A,-Parameters fur den Dunnschichtfall wird ebenfalls vorgeschlagen.

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We consider the transport properties in magnetic ultra-thin multilayers for electronic current in the plane of the surfaces. In the case of ultra-thin films, the conduction electron transport behavior is influenced by the shape and the thickness of a sample. The boundary conditions at the surface and interfaces lead to the electric charge density distribution across a film. We discuss the influence of sample thickness on some electronic properties like the Fermi energy, distribution of electrons and their spin polarisation. We justify some parameters introduced to the model potential whose values for spacer and ferromagnetic metals depend on the layer thickness. In this aspect the present approach constitutes improvement of Hood-Falicov model for the case of very thin layers.The discovery of giant magnetoresistance effects in Fe/Cr multilayers [1, 2] has triggered a large number of studies on the transport properties of magnetic multilayers. In spite of many experimental and theoretical investigations the description of the phenomenon is not completed and makes a challenge for many researchers [e.g. 3, 4]. In our paper [5] we have considered the transport properties in magnetic multilayers for electronic current in the layers parallel to the surfaces. This model is based on the effective s-band construction for the multilayer consisted of the spacer metallic and ferromagnetic, including s-d coupling, layers. In that model we have taken into account the spectrum energy of electrons in a trilayer and we have made the calculations of the Fermi level which is common for the effective s band electrons in tim whole sample [5]. The standard approach is determined by treating all of the valence electrons as being in a single free-electron like band with an isotropic effective mass, in each layer, i.e. spacer and ferromagnetic layer separately. In this paper we assume that a considered sample has a structure of three thin films which are characterised by means of the effective potentials reflecting the multilayered structure. Each of layers has got a crystal structure and the electronic density distribution is connected with the electric potential in a crystal assumed as a superposition of one-electronic potentials produced at the lattice sites. These sites are labeled by the two-dimensional vector j determined in the v-th layer parallel to the crystallographic plane and to the fihn surfaces. Each of n planes (v E (1, n)) *) Presented at ll

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