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Suche nach „[Mátéfi-Tempfli] [Stefan]“ hat 165 Publikationen gefunden
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    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    A. Milosavljević, Marinković B. P., Šević D., M. Mátéfi-Tempfli, Kolarž P., Z. Pešić, Víkor Gy., Piraux L., Stefan Mátéfi-Tempfli

    Guiding of low-energy electrons by highly ordered Al2O3 nanocapillaries

    Virtual Journal of Nanoscale Science & Technology (NanoUnion), vol. 15, no. 13

    2007

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    M. Mátéfi-Tempfli, V. Cros, C. Deranlot, Guillemet R., Bouzehouane K., L. Piraux, T. Blon, Stefan Mátéfi-Tempfli, Fusil S.

    Spin momentum transfer effects observed in electrodeposited Co/Cu/Co nanowires

    Journal of Applied Physics, vol. 102, no. 10

    2007

    DOI: 10.1063/1.2812677

    Abstract anzeigen

    Spin-transfer torque effects are reported in nanowires consisting in Co/Cu/Co trilayers electrodeposited on an anodic alumina template. Using a nanolithography process based on electrically controlled nanoindentation of the alumina template, we are able to investigate the spin transport properties of single nanowires at room temperature. For small applied magnetic fields, we have measured resistance changes above a critical direct-current (dc) injected current that corresponds to the change in resistance observed in the magnetoresistance curves at low current. We conclude that magnetic reversals are driven by a spin-polarized current. The critical current densities needed for the magnetization reversals are in the 107 A/cm2 range and the dependence of the critical currents with the applied field is consistent with the spin-transfer mechanism. For large applied magnetic fields, the differential resistance exhibits some peaks that we attribute to the onset of high-frequency excitations of the free-layer magnetization. According to the high density of electrodeposited nanowires in alumina templates, our results are promising for synchronized spin-transfer oscillators.

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    Zeitschriftenartikel

    V. Moshchalkov, M. Mátéfi-Tempfli, W. Vinckx, S. Michotte, J. Vanacken, L. Piraux, X. Ye, Stefan Mátéfi-Tempfli

    High field matching effects in superconducting Nb porous arrays catalyzed from anodic alumina templates

    Physica C: Superconductivity and its Applications, vol. 459, no. 1-2, pp. 5-10

    2007

    DOI: 10.1016/j.physc.2007.04.194

    Abstract anzeigen

    Vortex pinning in a superconducting Nb thin film deposited on an anodically grown alumina template is investigated. Anodic oxidation of aluminium layers permits under specific conditions the formation of highly ordered porous alumina, a membrane-like structure consisting of triangular arrays of parallel pores. Its pore diameter and interpore distance are set by careful tuning of the anodization parameters. A superconducting Nb thin film is deposited directly onto the alumina film. The porous alumina acts as a template and it allows Nb to form a periodic pinning array during its growth. Pinning force vs. field measurements derived from magnetization measurements, show matching effects in fields up to 1 T. We demonstrate that the anodic alumina template with 50 nm interpore spacing provides enhanced vortex pinning in a large field and temperature range.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    A. Milosavljević, Marinković B. P., Šević D., M. Mátéfi-Tempfli, Kolarž P., Z. Pešić, Víkor Gy., Piraux L., Stefan Mátéfi-Tempfli

    Guiding of low-energy electrons by highly ordered Al2O3 nanocapillaries

    Physical Review A, vol. 75, no. 3

    2007

    DOI: 10.1103/PhysRevA.75.030901

    Abstract anzeigen

    We report an experimental study of guided transmission of low-energy (200–350eV) electrons through highly ordered Al2O3 nanocapillaries with large aspect ratio (140nm diameter and 15μm length). The nanochannel array was prepared using self-ordering phenomena during a two-step anodization process of a high-purity aluminum foil. The experimental results clearly show the existence of the guiding effect, as found for highly charged ions. The guiding of the electron beam was observed for tilt angles up to 12°. As seen for highly charged ions, the guiding efficiency increases with decreasing electron incident energy. The transmission efficiency appeared to be significantly lower than observed for highly charged ions and, moreover, the intensity of transmitted electrons significantly decreases with decreasing impact energy.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    M. Mátéfi-Tempfli, V. Cros, Guillemet R., Bouzehouane K., Piraux L., Stefan Mátéfi-Tempfli, Fusil S., Renard K., Antohe V.

    Template-Grown NiFe/Cu/NiFe Nanowires for Spin Transfer Devices.

    Nano Letters, vol. 7, no. 9, pp. 2563-2567

    2007

    DOI: 10.1021/nl070263s

    Abstract anzeigen

    We have developed a new reliable method combining template synthesis and nanolithography-based contacting technique to elaborate current perpendicular-to-plane giant magnetoresistance spin valve nanowires, which are very promising for the exploration of electrical spin transfer phenomena. The method allows the electrical connection of one single nanowire in a large assembly of wires embedded in anodic porous alumina supported on Si substrate with diameters and periodicities to be controllable to a large extent. Both magnetic excitations and switching phenomena driven by a spin-polarized current were clearly demonstrated in our electrodeposited NiFe/Cu/ NiFe trilayer nanowires. This novel approach promises to be of strong interest for subsequent fabrication of phase-locked arrays of spin transfer nano-oscillators with increased output power for microwave applications.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    M. Mátéfi-Tempfli, V. Cros, C. Deranlot, Guillemet R., Bouzehouane K., L. Piraux, T. Blon, Stefan Mátéfi-Tempfli, Fusil S.

    Spin momentum transfer effects observed in electrodeposited Co/Cu/Co nanowires

    Virtual Journal of Nanoscale Science & Technology (NanoUnion)

    2007

    Abstract anzeigen

    Spin-transfer torque effects are reported in nanowires consisting in Co/Cu/Co trilayers electrodeposited on an anodic alumina template. Using a nanolithography process based on electrically controlled nanoindentation of the alumina template, we are able to investigate the spin transport properties of single nanowires at room temperature. For small applied magnetic fields, we have measured resistance changes above a critical direct-current (dc) injected current that corresponds to the change in resistance observed in the magnetoresistance curves at low current. We conclude that magnetic reversals are driven by a spin-polarized current. The critical current densities needed for the magnetization reversals are in the 107 A/cm2 range and the dependence of the critical currents with the applied field is consistent with the spin-transfer mechanism. For large applied magnetic fields, the differential resistance exhibits some peaks that we attribute to the onset of high-frequency excitations of the free-layer magnetization. According to the high density of electrodeposited nanowires in alumina templates, our results are promising for synchronized spin-transfer oscillators.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    V. Bayot, M. Mátéfi-Tempfli, L. Piraux, A. Vlad, S. Faniel, S. Melinte, Stefan Mátéfi-Tempfli

    Controlled growth of single nanowires within a supported alumina template

    Nanotechnology, vol. 17, no. 19, pp. 4873-4876

    2006

    DOI: 10.1088/0957-4484/17/19/016

    Abstract anzeigen

    A simple technique for fabricating single nanowires with well-defined position is presented. The process implies the use of a silicon nitride mask for selective electrochemical growth of the nanowires in a porous alumina template. We show that this method allows the realization of complex nanowire patterns as well as arrays of single nanowires with a precise position and spacing.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    V. Moshchalkov, M. Mátéfi-Tempfli, W. Vinckx, S. Michotte, J. Vanacken, L. Piraux, Stefan Mátéfi-Tempfli

    Vortex pinning in superconducting Nb thin films deposited on nanoporous alumina templates

    European Physical Journal B: Condensed Matter and Complex Systems, vol. 53, no. 2, pp. 199-203

    2006

    DOI: 10.1140/epjb/e2006-00358-7

    Abstract anzeigen

    We present a study of magnetization and transport properties of superconducting Nb thin films deposited on nanoporous aluminium oxide templates. Periodic oscillations in the critical temperature vs. field, matching effects in fields up to 700 mT and strongly enhanced critical currents were observed. These fields are considerably higher than those typical for periodic pinning arrays made by lithographic techniques, which reflects the benefits of nanostructuring superconductors by using self-organized growth. This method provides a periodic pinning potential with sub-100 nm spacing between the pinning centers, which enhances vortex pinning in broad field and temperature ranges.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    M. Szpakowska, O. Nagy, E. Plocharska-Jankowska, Stefan Mátéfi-Tempfli

    A New Approach to the Spectral Analysis of Liquid Membrane Oscillators by Gabor Transformation

    Journal of Physical Chemistry B, vol. 110, no. 1, pp. 289-294

    2006

    DOI: 10.1021/jp0557870

    Abstract anzeigen

    Liquid membrane oscillators very frequently have an irregular oscillatory behavior. Fourier transformation cannot be used for these nonstationary oscillations to establish their power spectra. This important point seems to be overlooked in the field of chemical oscillators. A new approach is presented here based on Gábor transformation allowing one to obtain power spectra of any kind of oscillations that can be met experimentally. The proposed Gábor analysis is applied to a liquid membrane oscillator containing a cationic surfactant. It was found that the power spectra are strongly influenced by the presence of various added substances.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    B. Sulik, S. Biri, M. Mátéfi-Tempfli, Z. Juhász, N. Stolterfoht, L. Piraux, Gy Vikor, J. Pálinkás, Stefan Mátéfi-Tempfli, I. Iván, F. Gáll, E. Fekete

    Guided transmission of slow Ne6+ ions through the nanochannels of highly ordered anodic alumina

    Nanotechnology, vol. 17, no. 15, pp. 3915-3919

    2006

    DOI: 10.1088/0957-4484/17/15/050

    Abstract anzeigen

    A highly ordered hexagonally close-packed nanochannels array was prepared using the self-ordering phenomena during a two-step anodization process of a high purity aluminium foil. The anodized aluminium oxide, with pore diameters of about 280 nm and interpore distances of about 450 nm was prepared as a suspended membrane of about 15 µm thickness on the aluminium frame to which it belongs. The Al2O3 capillaries were bombarded with 3 keV Ne6+ ions. The first results unambiguously show the existence of ion guiding observed at 5° and 7.5° tilt angles of the capillaries compared to the beam direction. To the best of our knowledge, such ion guiding effects of slow ions through hexagonally ordered nanochannels in alumina has not been reported previously.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    P. Smet, S. Michotte, P. Lommens, D. Poleman, L. Piraux, Z. Hens, Stefan Mátéfi-Tempfli, de Mello Donega, C., A. Meijerink

    Photoluminescence properties of Co2+-doped ZnO nanocrystals

    Journal of Luminescence, vol. 118, no. 2, pp. 245-250

    2006

    DOI: 10.1016/j.jlumin.2005.08.020

    Abstract anzeigen

    We performed photoluminescence experiments on colloidal, Co2+-doped ZnO nanocrystals in order to study the electronic properties of Co2+ in a ZnO host. Room temperature measurements showed, next to the ZnO exciton and trap emission, an additional emission related to the Co2+ dopant. The spectral position and width of this emission does not depend on particle size or Co2+ concentration. At 8 K, a series of ZnO bulk phonon replicas appear on the Co2+-emission band. We conclude that Co2+ ions are strongly localized in the ZnO host, making the formation of a Co2+d-band unlikely. Magnetic measurements revealed a paramagnetic behaviour.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    M. Szpakowska, O. Nagy, Stefan Mátéfi-Tempfli

    Chemical kinetic approach to the mechanism of coupled transport of Cu(II) ions through bulk liquid membranes

    Journal of Physical Chemistry A, vol. 109, no. 44

    2005

    DOI: 10.1021/jp055525y

    Abstract anzeigen

    Transport of copper(II) ions through bulk liquid membranes is studied in various experimental conditions. The results obtained are analyzed by using the concepts and methods of chemical kinetics. This approach allowed kinetic equations to be established which are sufficiently general to account for a large variety of transport kinetics (steady or nonsteady state, first or zeroth order, diffusion or reaction controlled, reversible or irreversible), to identify clearly the rate-determining steps, and to propose a detailed mechanism at the molecular level. The important role played by the interfaces is also demonstrated.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    M. Szpakowska, O. Nagy, E. Plocharska-Jankowska, Stefan Mátéfi-Tempfli

    On the possibility of molecular recognition of taste substances studied by Gabor analysis of oscillations

    Biophysical Chemistry, vol. 114, no. 2-3, pp. 85-93

    2005

    DOI: 10.1016/j.bpc.2004.10.004

    Abstract anzeigen

    A liquid membrane oscillator containing nitromethane as membrane material has been investigated. The influence of substances responsible for taste belonging to four classes (sweetness, saltiness, sourness and bitterness) on oscillation patterns of liquid membrane oscillators with cationic surfactant benzyldimethyltetradecylammonium chloride (BDMTAC) was examined. A new approach based on Gábor transformation is proposed for obtaining the power spectra of the observed oscillating signals and for establishing "fingerprints" of the investigated substances. It was shown that two-dimensional form of these power spectra might be used efficiently for this purpose.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    M. Mátéfi-Tempfli, L. Vila, S. Michotte, L. Piraux, M. Darques, Stefan Mátéfi-Tempfli, A. Encinas, F. Elhoussine

    Magnetic and superconducting nanowires

    Journal of Nanoscience and Nanotechnology, vol. 5, no. 3, pp. 372-389

    2005

    DOI: 10.1166/jnn.2005.062

    Abstract anzeigen

    This article is focused on the use of electrodeposition and of various nanoporous templates for the fabrication of metallic nanowires made from single metals (Ni, Co, Pb, Sn), alloys (NiFe, CoFe, CoPt), and multilayers (Co/Cu, NiFe/Cu). An overview is given of our recent studies performed on both magnetic and superconducting nanowires. Using different approaches entailing measurements on both single wires and arrays, numerous interesting physical properties have been identified in relation to the nanoscopic dimensions of these materials. Finally, various novel applications of the nanowires are also discussed.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    M. Mátéfi-Tempfli, L. Piraux, K. Yu-Zhang, Stefan Mátéfi-Tempfli, J. Mallet

    Electrodeposited L10 CoxPt1-x nanowires

    Journal of Physics D: Applied Physics, vol. 38, no. 6, pp. 909-914

    2005

    DOI: 10.1088/0022-3727/38/6/020

    Abstract anzeigen

    Arrays of face-centred cubic (fcc) CoxPt1 − x (0.45 < x < 0.55) nanowires were electrodeposited into thin film nanoporous alumina supported on a Si substrate. The heat treatment under specific conditions was then carried out in order to transform the fcc phase into the face-centred tetragonal or L10 ordered phase. The influence of both the phase transition and the temperature on the magnetic properties of CoxPt1−x nanowires has been studied. Coercive fields higher than 1 T (10 kOe) have been obtained at room temperature with ordered nanowires, 80 nm in diameter.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    M. Mátéfi-Tempfli, V. Cros, S. Michotte, K. Bouzehouane, C. Deranlot, J.-M. George, L. Piraux, L. Pereira, S. Fusil, C. Saul, Stefan Mátéfi-Tempfli

    Nanolithography based contacting method for electrical measurements on single template synthesized nanowires

    Nanotechnology, vol. 16, no. 12, pp. 2936-2940

    2005

    DOI: 10.1088/0957-4484/16/12/036

    Abstract anzeigen

    A reliable method enabling electrical measurements on single nanowires prepared by electrodeposition in an alumina template is described. This technique is based on electrically controlled nanoindentation of a thin insulating resist deposited on the top face of the template filled by the nanowires. We show that this method is very flexible, allowing us to electrically address single nanowires of controlled length down to 100 nm and of desired composition. Using this approach, current densities as large as 109 A cm−2 were successfully injected through a point contact on a single magnetic multilayered nanowire. This demonstrates that the technique is very promising for the exploration of electrical spin injection in magnetic nanostructures.

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    Zeitschriftenartikel

    M. Mátéfi-Tempfli, A. Palnichenko, J.-C. Charlier, J.-P. Issi, L. Piraux, Stefan Mátéfi-Tempfli

    Selective formation of diamond-like carbon coating by surface catalyst patterning

    Carbon, vol. 42, no. 8-9, pp. 1879-1882

    2004

    DOI: 10.1016/j.carbon.2004.03.004

    Abstract anzeigen

    Diamond-like carbon (DLC) materials are characterized by assemblies of varying ratios of sp3/sp2-bonded carbon and a lack of long range order of crystal structure. DLC is an extremely interesting industrial prospective material combining properties such as wear-, corrosion- and chemical-resistant qualities, resistance to stiction (i.e. a combination of stickness and friction), biocompatibility [1]. While silicon has been at the basis of modern electronics and the digital revolution, recent advances in microfabrication techniques have made possible the development of microscale devices that include different types of DLC coating [2]. Consequently, the process of controllable architecture of DLC coating is thus a major aspect for micro-electro-mechanical-systems manufacturing.

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    Zeitschriftenartikel

    S. Michotte, L. Piraux, Stefan Mátéfi-Tempfli, F. Peeters, D. Vodolazov

    Condition for the occurrence of phase slip centers in superconducting nanowires under applied current or voltage

    Physical Review B: Condensed Matter and Materials Physics, vol. 69, no. 9

    2004

    DOI: 10.1103/PhysRevB.69.094512

    Abstract anzeigen

    Experimental results on the phase slip process in superconducting lead nanowires are presented under two different experimental conditions: constant applied current or constant voltage. Based on these experiments we established a simple model which gives us the condition of the appearance of phase slip centers in a quasi-one-dimensional wire. The competition between two relaxations times (relaxation time of the absolute value of the order parameter τ|ψ| and relaxation time of the phase of the order parameter in the phase slip center τφ) governs the phase slip process. Phase slips, as periodic oscillations in time of the order parameter, are only possible if the gradient of the phase grows faster than the value of the order parameter in the phase slip center, or equivalently if τφ<τ|ψ|.

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    Zeitschriftenartikel

    S. Michotte, L. Piraux, Stefan Mátéfi-Tempfli, F. Peeters, D. Vodolazov

    Current-voltage characteristics of quasi-one-dimensional superconductors: an S-shaped curve in the constant voltage regime

    Physical Review Letters - moving physics forward, vol. 91, no. 15

    2003

    DOI: 10.1103/PhysRevLett.91.157001

    Abstract anzeigen

    Applying a constant voltage to superconducting nanowires we find that its I-V characteristic exhibits an unusual S behavior. This behavior is the direct consequence of the dynamics of the superconducting condensate and of the existence of two different critical currents: jc2 at which the pure superconducting state becomes unstable and jc1<jc2 at which the phase-slip state is realized in the system.

    NachhaltigEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    S. Michotte, L. Piraux, Stefan Mátéfi-Tempfli

    Investigation of superconducting properties of nanowires prepared by template synthesis

    Superconductor Science and Technology, vol. 16, no. 5, pp. 557-561

    2003

    DOI: 10.1088/0953-2048/16/5/302

    Abstract anzeigen

    We report on the transport properties of single superconducting lead nanowires grown by an electrodeposition technique, embedded in a nanoporous track-etched polymer membrane. The nanowires are granular, have a uniform diameter of ~40 nm and a very large aspect ratio (~500). The diameter of the nanowires is small enough to ensure a one-dimensional superconducting regime in a wide temperature range below Tc. The non-zero resistance in the superconducting state and its variation caused by fluctuations of the superconducting order parameter were measured versus temperature, magnetic field, and applied dc current (or voltage). The current-induced breakdowns in the voltage–current characteristics may be explained by the formation of phase slip centres. Moreover, dc voltage driven measurements reveal the existence of a new S-shape behaviour near the formation of these phase slip centres.