42 research outputs found

    Quadrupolar XMCD at the Fe K -edge in Fe phthalocyanine film on Au: Insight into the magnetic ground state

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    The observation of an anomalous quadrupolar signal in x-ray magnetic circular dichroism (XMCD) at the Fe K-edge of iron phthalocyanine (FePc) films is reported. All ground states previously suggested for FePc are incompatible with the experimental data. Based on ab initio molecular orbital multiplet calculations of the isolated FePc molecule, we propose a model for the magnetic ground state of the FePc film that explains the XMCD data and reproduces the observed values of the orbital moments in the perpendicular and planar directions

    Molecular tilting and columnar stacking of Fe phthalocyanine thin films on Au(111)

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    Scanning tunneling microscopy and x-ray absorption spectroscopic results at the Fe K edge of Fe phthalocyanine (FePc) thin films grown on Au substrates, together with theoretical calculations, allow us to refine the structure of the film. In particular, we show that the columnar stacking of the FePc molecules is different from that found in bulk a and ß phases. Moreover, the molecules do not lay parallel to the surface of the substrate. These structural findings are relevant to understand magnetism of FePc films

    The influence of the boundary resistivity on the proximity effect

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    We apply the theory of Takahashi and Tachiki in order to explain theoretically the dependence of the upper critical magnetic field of a S/N multilayer on the temperature. This problem has been already investigated in the literature, but with a use of an unphysical scaling parameter for the coherence length. We show explicitely that, in order to describe the data, such an unphysical parameter is unnecessary if one takes into account the boundary resisitivity of the S/N interface. We obtain a very good agreement with the experiments for the multilayer systems Nb/Cu and V/Ag, with various layer thicknesses.Comment: 12 pages, 5 figure

    LASER IRRADIATION EFFECTS IN SUPERCONDUCTORS

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    Nous avons Ă©tudiĂ© le comportement d'un SQUID (Superconducting Quantum Interference Device) Ă  couche mince et d'une boucle supraconductrice bi-mĂ©tallique sous irradiation d'une lumiĂšre laser. Nous trouvons que les rĂ©sultats expĂ©rimentaux peuvent ĂȘtre expliquĂ©s par un simple Ă©chauffement. Cette interprĂ©tation ne suppose pas l'existence d'une rĂ©partition de quasi-particules qui soit simultanĂ©ment hors-Ă©quilibre et non-thermique. Nous trouvons Ă©galement que les effets thermiques empĂȘchent l'observation d'un comportement collectif Ă  basse tempĂ©rature suggĂ©rĂ© par Bari et Sukhanov.We have studied the behaviour of a thin film Superconducting Quantum Interference Device (SQUID) and of a bi-metallic superconducting loop under laser light irradiation. We find that the experimental data can be explained by simple thermal heating without assuming the existence of non-thermal non-equilibrium quasiparticle distribution. We also find that the observation of collective behaviour at low temperature as suggested by Bari and Sukhanov will be hindered by thermal effects

    UPPER CRITICAL FIELD OF Mo-Ni HETEROSTRUCTURES

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    Upper critical field and its anisotropy have been measured on two very short wavelength Mo-Ni heterostructures of different degrees of perfection, lambda = 13.8A (disordered structure) and lambda = 16.6A (layered structure). In both cases the parallel critical field has an unexpected temperature dependence, a large and temperature dependent anisotropy, and over 60% enhancement over the Clogston-Chandrasekhar limit. Data are fit to the Werthamer-Helfand-Hohenberg theory and the spin-orbit scattering times are found to be 1.79 x 10 T s and 2 x 10 T s, respectively
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