The proximity effect between a superconductor ͑S͒ and a weak ferromagnet ͑F͒ in sputtered Nb/ Pd 0.86 Ni 0.14 bilayers has been studied. The dependence of the critical temperature on the Sand F-layer thicknesses can be interpreted in the framework of recent theoretical models and yields reasonable numbers for the exchange energy of the ferromagnet and the interface transparency of the S/F barrier.

Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. We combine point contact spectroscopy with specific heat measurements to probe the superconducting state in noncentrosymmetric Nb 0.18 Re 0.82 single crystals. The conductance spectra clearly exhibit a two-peak structure that is well reproduced within a two-band model with isotropic gaps in the spectrum. Such an observation is confirmed by distinct features of the specific heat both at low temperatures and in the range approaching the transition to the normal state. The analyses provide convincing evidence that the two-gap superconducting pairing is a robust feature of Nb 0.18 Re 0.82 .

Robust porous silicon substrates were employed for generating interconnected networks of superconducting ultrathin Nb nanowires. Scanning electron microscopy analysis was performed to investigate the morphology of the samples, which constitute of polycrystalline single wires with grain size of about 10 nm. The samples exhibit nonzero resistance over a broad temperature range below the critical temperature, fingerprint of phase slippage processes. The transport data are satisfactory reproduced by models describing both thermal and quantum fluctuations of the superconducting order parameter in thin homogeneous superconducting wires

By measuring I–V characteristics as a function of the temperature and the external magnetic field, we have analyzed the static and dynamic properties of the vortex lattice in Nb/Pd0.84Ni0.16 bilayers. In particular, the critical current density Jc for the onset of the vortex motion and the dynamic instability of the moving vortex lattice at high driving currents have been studied and compared to the results obtained in a single Nb film. We find that Jc is smaller in the bilayers than in the single superconducting film due to the smaller value of the superconducting order parameter in the bilayers. The critical velocity v* for the occurrence of the instability is larger in the S/F bilayers than in the single S layer. However, the quasiparticle energy relaxation rate extracted from v* is almost temperature-independent, implying that a different relaxation mechanism plays a role in the Nb/Pd0.84Ni0.16 bilayers.

The morphology of abrupt bursts of magnetic flux into superconducting films with engineered periodic pinning centers (antidots) has been investigated. Guided flux avalanches of thermomagnetic origin develop a tree-like structure, with the main trunk perpendicular to the borders of the sample, while secondary branches follow well-defined directions determined by the geometrical details of the underlying periodic pinning landscape. Strikingly, we demonstrate that in a superconductor with relatively weak random pinning, the morphology of such flux avalanches can be fully controlled by proper combinations of lattice symmetry and antidot geometry. Moreover, the resulting flux patterns can be reproduced, to the finest details, by simulations based on a phenomenological thermomagnetic model. In turn, this model can be used to predict such complex structures and to estimate physical variables of more difficult experimental access, such as the local values of temperature and electric field.