Solid State Phenomena Vols. 233-234

Abstract: Amorphous Со-Р and Co-Ni-P films fabricated by chemical deposition under the same conditions are investigated. It is demonstrated that the phosphorous content in the Co-Ni-P exceeds that in the Со-Р films by 1.5−2%. The atomic force microscopy analysis of the surface morphology shows that incorporation of Ni atoms in the Со−Р alloy leads to coarsening of grains due to the higher rate of deposition of Ni atoms as compared with the rate of deposition of Со atoms. The reduction of the dispersion of the polar Kerr effect saturation field in the Со-Ni-P films is attributed to ordering of Сo-Ni atomic pairs.

Abstract: In the work, magnetization-induced second-harmonic generation (MSHG) effect has been appliedto investigate the magnetization distribution changes, induced by ion implantation into thethin surface layer of garnet film.The studies were performed on the (111)-orientedepitaxial garnet film (YSmLuCa)$_3$(FeGa)$_5$O$_{12}$ implanted with $1.5\times10^{16}$~cm$^{-2}$dose of H$_2^+$ ions at $60$~keV energy. The measurements of the MSHG effectwere performed as a function of amplitude of perpendicular external magnetic field. The observed complex field dependencesof the remagnetization processes for the implanted garnet film studied were described in theframe of a phenomenological model developed. The model of the MSHG effect allows to performdecomposition of measured dependences on separate contributions originating from magnetizationcomponents related to implanted and unimplanted film volumes.

Abstract: Nanocomposite Fe_x(Al₂O₃)_100-x films with concentration gradient along the long axis of the samples (40 mm) have been obtained by sputter deposition technique and investigated. Based on the electric and magnetoresistive investigations the gradient Fe_x(Al₂O₃)_100-x samples in which concentration of one edge of the sample is smaller than concentration of a percolation threshold while concentration of opposite edge of this sample is upper the threshold have been determined. Influence of the heat flow direction on the thermoelectric power of the gradient samples has been investigated. Hysteresis of the thermoelectric power is observed when temperature gradient direction is changed.

Abstract: Surface structure and magnetic properties of thin films of the FINEMET-type alloy modificated by Mo (FeCuNbSiBMo) were studied in the aim of establishing of their dependence on heat treatment conditions. The thicknesses of the films were varied from 10 to 800 nm. Dependence of the microstructure of the films surface on the annealing temperature was analyzed using scanning probe microscopy. Parameters of the topography features were estimated as a function of the films thickness and annealing temperature. Magnetic hysteresis loops were measured using vibrating sample magnetometer and discussed in the focus of surface and thickness influences.

Abstract: The magnetic static permeability of sputtered FeCuNbSiB and electrodeposited NiFe patterns with thicknesses varying from 0.1 to 8 μm has been studied. The permeability varies proportionally with the pattern size/thickness ratio, like for uniformly magnetized patterns. Different hypothesis on this variation have been investigated and a critical analysis favors a demagnetizing effect. The comparison between experimental results and the theoretical value of the demagnetizing factor of squares plates confirms MOKE imaging, i.e. large magnetic domains but a non-uniform magnetization in the samples.

Abstract: Abstract. We prepared, under vacuum and onto monocrystalline silicone and glass substrates, series of CoxCr1-x thin films, with x ranging from 0.80 to 0.88. The structural and magnetic properties of the as deposited films have been performed using Rutherford backscattering spectrometry (R.B.S.), X-ray diffraction (X.R.D.), Alternating Gradient Field Magnetometer (A.G.F.M.), and Brillouin Light Spectrometry (B.L.S.) techniques. Once the films being annealed under vacuum, for 1 h at 700°C, in a pre-heated furnace, their structural and magnetic properties have been performed, by these tools, as well. Significant results have been found. The as deposited films present only an HCP structure and show a preferred orientation. The annealed films present both HCP and FCC structures. The annealed films possess cell parameters greater than the bulk ones which infer that they are under a tensile stress. The cell parameters of the as deposited films are lower than the bulk ones which infer that they are under a compressive stress. Up to the annealing temperature the films are still ferromagnetic and some decrease of the magnetic moment is noticed. In addition, coercivity and squareness have been strongly improved in the annealed films comparatively to the as deposited films. Moreover, the stiffness constant, computed using Brillouin light scattering measurements and after adjustment of theoretical and experimental results, is found to be far lesser than pure Co one. These results and others will be presented and discussed.

Abstract: The influence of the Co doping on the properties of zinc oxide films was investigated. The films were grown by oxygen and water assisted metal organic chemical vapor deposition (MOCVD). The large positive magnetoresistance (PMR) was observed in Co doped films at low temperatures while the negative magnetoresistance was observed in undoped ZnO films deposited under the same conditions. The relative variation of resistivity was comparable in the films grow by oxygen and water assisted MOCVD although the resistivity and its temperature dependence were significantly different. The magnitude of PMR increases with an increase of the Co content and with the decrease of temperature.

Abstract: Amorphous hydrogenated carbon thin films were deposited on Si and glassceramics substrates by reactive ion-plasma magnetron sputtering. Thin films were without (a-C:H) and with Ni nanoparticles (a-C:H:Ni). Measurement of absorption coefficient in 220-850 nm spectral range using spectrophotometer and following approximation applying of Tauc method shows that obtained a-C:H thin films material has near 3.6 eV optical band gap and confirmed that this material is amorphous semiconductor. Thin films with Ni nanoparticles have a high complex permittivity ε* and permeability μ* (ε′ ≈ 1000–10000, ε′′ ≈ 100–1500, μ′ ≈ 10–70, μ′′ ≈ 0.4-10). Some magnetic parameters of thin films were determined.

Abstract: The problem of the superconductivity of σ electrons in compounds with a honecomb structure has been analyzed. The equations of superconductivity and the phase diagram have been obtained under the assumption that the Hubbard energy is the largest energy parameter.

Abstract: We present resistivity measurements of the upper critical field as a function of temperature for Nd_2-xCe_xCuO_4+δ/SrTiO₃ single crystal films near antiferromagnetic-superconducting phase boundary (x = 0.14) in magnetic fields up to 90kOe at temperatures down to 0.7K. The data are well described by a two-band/two-gap model for a superconductor in the dirty limit.