Publications

Indium-doped zinc oxide thin films deposition was performed by the sol-gel technique using homogeneous and stable solutions of zinc acetate 2-hydrate and indium chloride in ethanol Films were spin coated onto glass substrates After drying and after a heat treatment at 450 degrees C highly transparent (80%-90%) films were obtained The effect on the structural morphological optical and electrical thin films properties of the dopant concentration was investigated The temperature dependencies of the electrical conductivity under vacuum and in open atmosphere were analysed and discussed (C) 2010 Elsevier B V All rights reserved

Two-component superconductivity based on the two-band superconductor has a functional topology such as an inter-band phase difference soliton (i-soliton) to realize topological electronics (topolonics). Many gauge field theories are applied to investigate the topology of two-band superconductivity. To ease experimental and electronics applications, these theories should be refined. Weinberg-Salam theory and SU(2) (two-dimensional special unitary symmetry) gauge field theory are proper starting points. An effective extra force field because of the crystal structure and inter-band Josephson interaction, rather than spontaneous symmetry breaking, simplifies the conventional gauge field theory. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.

The temperature T variation of the normalized magnetization relaxation rate S in high-temperature superconductors (HTS) with strong vortex pinning exhibits a maximum in the low-T range. This was reported for various HTS, and the origin of the faster relaxation at low T appearing in standard magnetization relaxation measurements was usually related to specific pinning properties of the investigated specimens. Since the observed behaviour seems to be characteristic to all HTS with enhanced pinning (generated by random and/or correlated disorder), we show that the S(T) maximum can be explained in terms of classic collective vortex creep. The influence of thermo-magnetic instabilities in the low-T range is also evidenced. The collective (elastic) creep regime is generated by the T dependent macroscopic currents induced in the sample during standard magnetization measurements. (C) 2010 Elsevier B.V. All rights reserved.

We have fabricated and studied quasi-multilayered thick YBa2Cu3O7-delta (YBCO) films composed of several YBCO layers Interspaced with quasi-layers of non-superconducting YBa2Cu3Ox nanodots grown by Pulsed Laser Deposition on SrTiO3 (100) substrates Magnetization J(c)(B) at 773 K for these thick films showed significant improvement as compared to pure YBa2Cu3O7-delta films of same or even smaller thickness A high J(c)(B) in our quite thick films (1 mu m to 6 mu m) provides a very high total critical current per centimetre of the film width Ic-w Critical current as high as 830 A per cm width in self field and 77 3 K was achieved in 5 mu m thick quasi-multilayer film with non-superconducting YBa2Cu3Ox nanodots Frequency-dependent susceptibility measurements showed also an increase in the pinning potential The angular dependence of Ic-w at 86 5 K in 3 T shows a clear indication of anisotropic pinning centres aligned along the c-direction (C) 2010 Elsevier B V All rights reserved

We have investigated the superconducting properties of Ag/YBa2Cu3O7-x thick multilayers grown by Pulsed Laser Deposition, and found that the artificial pinning centres induced by Ag nanodots lead to a significant increase in critical current, especially in high applied magnetic fields. Transmission Electron Microscopy showed a columnar growth of YBa2Cu3O7-x, induced by Ag nanodots, while angle-dependent transport measurements revealed the existence of strong, both isotropic and c-axis correlated, artificial pinning centres. (C) 2010 Elsevier B.V. All rights reserved.

A FePt-based hard-magnetic nanocomposite of exchange spring type was prepared by isothermal annealing of melt-spun Fe52Pt28Nb2B18 (atomic percent) ribbons. The relationship between microstructure and magnetic properties was investigated by qualitative and quantitative structural analysis based on the x-ray diffraction, transmission electron microscopy, and Fe-57 Mossbauer spectrometry on one hand and the superconducting quantum interference device magnetometry on the other hand. The microstructure consists of L1(0)-FePt hard-magnetic grains (15-45 nm in diameter) dispersed in a soft magnetic medium composed by A1 FePt, Fe2B, and boron-rich (FeB)PtNb remainder phase. The ribbons annealed at 700 degrees C for 1 h exhibit promising hard-magnetic properties at room temperature: M-r/M-s=0.69; H-c=820 kA/m and (BH)(max)=70 kJ/m(3). Strong exchange coupling between hard and soft magnetic phases was demonstrated by a smooth demagnetizing curve and positive delta M-peak in the Henkel plot. The magnetic properties measured from 5 to 750 K reveals that the hard characteristics remains rather stable up to 550 K, indicating a good prospect for the use of these permanent magnets in a wide temperature range. (C) 2010 American Institute of Physics. [doi:10.1063/1.3504245]

In core-shell systems with non-magnetic core and magnetic shell the electron transport and magnetic properties are expected to show enhanced behavior due to the particular morpho structural features of the conductive and magnetic regions This may lead to novel advanced GMR materials and spin valves This is the case of core-shell Ag-Co colloidal nanoscale particles that organize into regular arrays An insight on the structure and morphology of the newly synthesized Ag-Co nanoparticles deposited on different substrates will be presented The influence of the substrate on different morphologies and organization dynamics is discussed It is shown that the magnetic behavior of the Ag-Co nanoparticles is highly influenced by the corona-like morphology of Co shell chemical environment of the magnetic atoms and by the fact that they exhibit strongly reduced coordination due to the surface states (C) 2010 Elsevier Masson SAS All rights reserved

The synthesis of the chalcogenide glass (Ge5As2S13) doped by Nd3+ has been carried out. The bulk glass develops a small amount of Nd2O3 and As2O3 crystallites besides some amount of (NdCl3)*6H(2)O crystalline phase initially introduced during synthesis. The optical absorption spectra demonstrate the presence of the Nd3+ both in the amorphous phase and in crystalline combinations. The formation of Nd2O3 crystallites was explained by the reaction of water with neodymium chloride. The presence of As2O3 is due to the oxidation of As from the glass during preparation.

In this study the Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique was used to prepare thin films from a low melting point (< 100 degrees C) organic compound (benzil). Optical properties of the films have been investigated by UV-VIS, FTIR and PL spectroscopy. Details about crystallinity were obtained by XRD measurements. FTIR spectra have confirmed the preservation of the chemical structure of the compound during the deposition process. SEM and AFM investigation have evidenced a topography of the MAPLE deposited films characterized by different grain size depending on the deposition conditions. Second harmonic generation measurements have revealed that the MAPLE deposited benzil films have preserved the optical nonliniar properties of the bulk crystalline benzil.

As2S3 on Ag heterostructures deposited onto microscope glass substrates have been prepared. The quality of the hetero-structures has been investigated by careful analysis of the scanning electron microscope pictures taken on the native cross-sections, produced after the vacuum deposition sequence and various green laser irradiation times. The As2S3 layer is not uniformly grown, but reveals a columnar-like structure and multi-scale aggregation.