MAGNETIC PROPERTIES OF COMPOSITIONALLY MODULATED FILMS

The compositionally modulated Cu/Ni, Cu/Co and Cu/Fe films have been prepared where both the wavelength of modulation and average composition vary. The magnetic properties were measured in the temperature range 4.2-850 K

Strong and Weak Interlayer Exchange Coupling in V/Fe Multilayers

The $d_{V}-V$/0.6 nm-Fe multilayers with constant thickness sublayers were prepared onto naturally oxidised Si(100) substrate using UHV (5× $10^{-10}$ mbar) DC/RF magnetron sputtering. Results showed that the saturation field of the V/Fe multilayers oscillate with antiferromagnetic interlayer exchange coupling peaks near the V spacer thickness of about 1.3, 1.6, 2.05 nm. Furthermore, all the samples with vanadium layer thickness near local maxima of the antiferromagnetic coupling show zero remanence. The short period of the antiferromagnetic peak oscillations is due to indirect Ruderman-Kittel-Kasuya-Yosida (RKKY)-type coupling of the Fe layers across vanadium spacer. The absence of the antiferromagnetic peaks in the very strongly coupled region (below $d_{V}$ ≈ 1 nm) could be explained by direct ferromagnetic exchange coupling of the Fe layers due to magnetic polarization of V atoms near V-Fe interface

Electronic, Magnetic and Transport Properties of YCo3\text{}_{3}B2\text{}_{2} Compound

We studied the electronic, magnetic and transport properties of the hexagonal YCo$\text{}_{3}$B$\text{}_{2}$ compound. The electronic structure was studied by X-ray photoemission spectroscopy and ab initio self-consistent tight binding linear muffin tin orbital method. We found a good agreement between the experimental X-ray photoemission spectroscopy valence band spectra and theoretical calculations. Theoretical calculations showed that the YCo$\text{}_{3}$B$\text{}_{2}$ is a paramagnet in agreement with experimental results. Electrical resistivity at low temperatures shows a T$\text{}^{2}$ dependence, implying that the scattering by the spin fluctuactions is dominant in this temperature range

Growth and Structural Characterisation of V/Fe Multilayers

The (110) oriented V/Fe multilayers were prepared at room temperature using UHV magnetron sputtering. As a substrate we have used Si(100) wafers with an oxidised surface. The surface chemical composition and the cleanness of all layers was checked in situ, immediately after deposition, transferring the samples to an UHV analysis chamber equipped with X-ray photoelectron spectroscopy. The structure of the multilayers has been studied ex situ by low- and high-angle X-ray diffraction. The modulation wavelength was determined from the spacing between satellite peaks in the X-ray diffraction patterns. Results were consistent with the values obtained from total thickness divided by the number of repetitions. Growth of the Fe (V) on 1.6 nm V (Fe) underlayer was studied by succesive deposition and X-ray photoelectron spectroscopy measurements starting from 0.2 nm of Fe (V) layer, respectively. From the exponential variation of the X-ray photoelectron spectroscopy Fe 2p and V 2p integral intensities with increasing layer thickness we conclude that the Fe and V sublayers grow homogeneously in the planar mode

Oxidation Kinetics of Thin and Ultrathin Fe Films

We have studied oxidation kinetics of Fe thin films under atmospheric conditions using the fact that metallic iron is a ferromagnet but ultrathin natural iron oxides are practically nonmagnetic at room temperature. As a consequence, oxidation is associated with a loss in ferromagnetism. Fe thin films were deposited onto 1.5 nm V thick buffer layer using UHV magnetron sputtering. As a substrate we have used Si(100) wafers with an oxidised surface. Results show that all samples with an initial Fe thickness greater than 6 nm oxidize practically instantaneously, whereby a constant amount of 2.5 nm of metal is transformed into oxides. For iron thickness lower than 6 nm the time constant for oxidation increases considerably reaching a value of 30 days for the initial Fe thickness equal to 4 nm

Electronic Properties of In Situ Prepared Nanocrystalline Fe-Ni-Ti Alloy Thin Films

In this contribution we study experimentally the electronic properties of nanocrystalline Fe-Ni-Ti alloy thin films using X-ray photoelectron spectroscopy. The structure of the samples has been studied by X-ray diffraction. Their bulk chemical compositions were measured using X-ray fluorescence method. The surface chemical composition and the cleanness of all samples were checked in situ, immediately after deposition, transferring the samples to an UHV analysis chamber equipped with X-ray photoelectron spectroscopy. X-ray diffraction studies revealed the formation of nanocrystalline Fe-Ni-Ti alloy thin films at a substrate temperature of about 293 K. In situ X-ray photoelectron spectroscopy studies showed that the valence bands of nanocrystalline samples are broader compared to those measured for the polycrystalline bulk alloys. Such modifications of the valence bands of the nanocrystalline alloy thin films could influence on their hydrogenation properties

XPS Valence Band Studies of LaNi5−xMxLaNi_{5-x}Mₓ (M = Al, Co; x = 0, 1) Alloy Thin Films

$LaNi_{5-x}Mₓ$ (M = Al, Co) alloy thin films were prepared onto oxidised Si(100) substrates in the temperature range of 285-700 K using UHV magnetron co-sputtering. The surface chemical composition and valence bands of all the alloy thin films were measured in situ, immediately after deposition, transferring the samples to an UHV analysis chamber equipped with X-ray photoelectron spectroscopy. Results showed that the shape of the valence bands measured for the polycrystalline samples is practically the same compared to those obtained theoretically from ab initio band structure calculations. On the other hand, the X-ray photoelectron spectroscopy valence bands of the nanocrystalline thin films (especially LaNi₄Co) are considerably broader compared to those measured for the polycrystalline samples. This is probably due to a strong deformation of the nanocrystals. Therefore, the different microstructure observed in polycrystalline and nanocrystalline alloy thin films leads to significant modifications of their electronic structure