Publications

The laser pyrolysis became a useful tool, providing various ways, in production of nano materials. The iron Mossbauer spectroscopy is one very accurate method in evidencing the physical properties and related processes in the nano scale compounds. The effect of pressure, laser spot area and induced combustion, of gas mixture and laser power on the phase composition and inside particle distribution, grain size as well as the related phenomena were investigated by temperature dependent Mossbauer spectroscopy. A selection of most relevant properties is presented and discussed in details.

The structural peculiarities of titanium oxide films formed by pulsed laser deposition have been investigated. A pure titanium target was irradiated by a Nd:YAG laser (355 and 532 nm). The work studied the influence of the beam wavelength, and oxygen pressure (20, 40, 80, and 160 mTorr) upon the layer structure. The films deposited at room temperature were partly crystalline. The crystalline fraction was a mixture of titanium sub-oxides. The 532 nm wavelength seems to favour the oxidation of titanium leading to TiO(2) formation even at room temperature. After annealing, crystalline TiO(2-) anatase formed at both irradiation wavelengths, but only at low oxygen pressures (20 and 40 mTorr). The best crystallization occurs in the layers deposited at the lowest oxygen pressure (20 mTorr), at both laser beam wavelengths; most anatase formed in the sample obtained at 20 mTorr, 532 nm. At 20 mTorr the films were compact, for both wavelengths, but also tilted or randomly distributed columnar grains were observed at higher pressure. The films deposited with 355 nm, were thinner than those with 532 nm; at 355 nm the thickness decreased at higher pressure, while at 532 nm the dependence was opposite.

Films of different thickness (50,100,150 and 200 nm) were deposited by thermal evaporation in vacuum on two types of substrates glass and ITO. The deposition was performed under a pressure of 10(-6) mB with a rate of 0.25 nm/s. Films surface investigations showed morphological and structural changes in function of films thickness and the nature of the substrate. Films optical transmission was analysed in the 280-1600 nm spectral range and the electrical measurements were done in low vacuum (10(-1):10(-2) mB) and in dark. (c) 2009 Elsevier Ltd. All rights reserved.

Multiwall carbon nanotubes, as indicated by electron microscopy and spectroscopy, were grown over a novel Co(5 wt.%)/ZnO catalyst by using a cold wall radio-frequency catalytic chemical vapor deposition method. The nanotubes were found to have a rather narrow diameter distribution, which can be explained by the formation over the ZnO support particles of uniform Co clusters, as shown by high resolution transmission electron microscopy studies. The growth of carbon nanotubes over such a support could represent a fast and reliable method to develop in one step 3D ZnO-CNTs heterogeneous composites of any size or shape, for use in advanced applications. (c) 2009 Elsevier B.V. All rights reserved.

There are four topologically different paths to interchange two single-component winding vortices in a two-band superconductor having a weak inter-band interaction, where each band has its own superconducting component and its own phase, theta(v), other than the ordinary quantum phase, Theta (v is the index of the band and Theta is defined at the region of theta(1) = theta(2).). The acquired phase for the interchange of two single-winding vortices depends on the path, and three values Theta(soliton),-Theta(soliton) and 0, are observed. Theta(soliton) is the phase-slip accompanying the inter-band phase difference soliton (i-soliton). The interchange requires the creation and annihilation of the i-soliton and gives rise to an ambiguity in the statistics. (C) 2008 Elsevier B.V. All rights reserved.

An X-ray magnetic circular dichroism (XMCD) study performed at the rare-earth L-2,L-3-edges in the RxR'Al-1-x(2) compounds is presented. It is shown that both R and R' atoms contribute to the XMCD recorded at the L-edges of the selected rare-earth, either R or R'. The amplitude of the XMCD signal is not directly correlated to the magnetization or to the value of the individual (R, R') magnetic moments, but it is related to the molecular field acting on the rare-earth tuned in the photoabsorption process. This result closes a longstanding study of the origin of the XMCD at the L-edge of the rare-earths in multi-component systems, allowing a full understanding of the exact nature of these signals.

The subsystems of the CMS silicon strip tracker were integrated and commissioned at the Tracker Integration Facility (TIF) in the period from November 2006 to July 2007. As part of the commissioning, large samples of cosmic ray data were recorded under various running conditions in the absence of a magnetic field. Cosmic rays detected by scintillation counters were used to trigger the readout of up to 15% of the final silicon strip detector, and over 4.7 million events were recorded. This document describes the cosmic track reconstruction and presents results on the performance of track and hit reconstruction as from dedicated analyses.

Using an electrochemical method have been produced NiCu thin films for magnetic applications. The recent development of first-order reversal curve (FORC) diagrams has allowed the detailed investigation of coercivity spectra, interaction and domain states of magnetic thin films. Their magnetic properties have been investigated by Micro Mag (TM) 3900 Vibrating Sample Magnetometer (VSM) and are discussed.

The X (9.8 GHz)-band electron paramagnetic resonance (EPR) properties of substitutional Mn2+ ions in high quality cubic ZnS single crystals grown from PbCl2 flux have been thoroughly investigated. Accurate spin Hamiltonian (SH) parameters: g = 2.002 25 +/- 0.000 06; a = (7.987 +/- 0.008) x 10(-4) cm(-1) and A = -(63.88 +/- 0.02) x 10(-4) cm(-1) were obtained by simulation and fitting to the experimentally allowed transitions recorded for the magnetic field aligned within +/- 0.25 degrees along the main crystal axes. The normally forbidden hyperfine M = + 1/2 -1/2, Delta m = +/- 1 transitions were also observed. Their position was found to be in agreement, within the experimental accuracy of Delta H = +/- 0.01 mT, with calculations using the same SH parameters. The angular variation of the ratios of the intensities of the central forbidden to the allowed transitions could be accounted for only by including an additional constant contribution. The observed line broadening of the M = +/- 1/2 +/- 3/2 and +/- 3/2 +/- 5/2 fine structure transitions and their line width variation in a (110) plane have been quantitatively described by considering a random distribution of lattice strains at the Mn2+ impurity ions. The influence of the forbidden transitions and line broadening on the EPR spectra line shape of the Mn2+ ions in cubic ZnS crystalline powders is also examined.