A set of poly(propylene) composites containing different amounts of copper nanoparticles (CNP) were prepared by the melt mixed method and their antimicrobial behavior was quantitatively studied. The time needed to reduce the bacteria to 50% dropped to half with only 1 v/v % of CNP, compared to the polymer without CNP. After 4 h, this composite killed more than 99.9% of the bacteria. The biocide kinetics can be controlled by the nanofiller content; composites with CNP concentrations higher than 10 v/v % eliminated 99% of the bacteria in less than 2 h. X-ray photoelectron spectroscopy did not detect CNP at the surface, therefore the biocide behavior was attributed to copper in the bulk of the composite.

The optical properties of hydrogen exposed palladium (Pd) and palladium oxide (PdO) thin films are calculated from reflectance and transmittance measurements in the visible and near infrared range (400–900nm). The time evolution of the films’ optical constants when exposed to hydrogen is shown. The real part of palladium’s refractive index increases about 5%, whereas the imaginary part decreases nearly 15% after hydrogen absorption. The Pd films’ resistance also increased upon hydrogen absorption, as expected. Pd oxide reduces to metallic palladium upon hydrogenation, showing a dramatic change in all the properties. The palladium films’ resistance initially decreases after a first exposure to 5Torr of hydrogen, and this is tentatively explained by the reaction of hydrogen with impurities trapped in the films.

We present a thorough investigation by magneto-optical imaging of the magnetic flux penetration in Nb thin films with lithographically defined border indentations. We demonstrate that discontinuity lines (d-lines), caused by the abrupt bending of current streamlines around the indentations, depart from the expected parabolic trend close to the defect and depend on the shape and size of the indentation as well as on the temperature. These findings are backed up and compared with theoretical results obtained by numerical simulations and analytical calculations highlighting the key role played by demagnetization effects and the creep exponent n. In addition, we show that the presence of nearby indentations and submicrometer random roughness of the sample border can severely modify the flux front topology and dynamics. Strikingly, in contrast to what has been repeatedly predicted in the literature, we do not observe that indentations act as nucleation spots for flux avalanches, but they instead help to release the flux pressure and avoid thermomagnetic instabilities.

Local polarization of a magnetic layer, a well-known method for storing information, has found its place in numerous applications such as the popular magnetic drawing board toy or the widespread credit cards and computer hard drives. Here we experimentally show that a similar principle can be applied for imprinting the trajectory of quantum units of flux (vortices), travelling in a superconducting film (Nb), into a soft magnetic layer of permalloy (Py). In full analogy with the magnetic drawing board, vortices act as tiny magnetic scribers leaving a wake of polarized magnetic media in the Py board. The mutual interaction between superconducting vortices and ferromagnetic domains has been investigated by the magneto-optical imaging technique. For thick Py layers, the stripe magnetic domain pattern guides both the smooth magnetic flux penetration as well as the abrupt vortex avalanches in the Nb film. It is however in thin Py layers without stripe domains where superconducting vortices leave the clearest imprints of locally polarized magnetic moment along their paths. In all cases, we observe that the flux is delayed at the border of the magnetic layer. Our findings open the quest for optimizing magnetic recording of superconducting vortex trajectories.Quantum magnetic flux units in type-II superconductors can be regarded as small solenoids, producing localized magnetic field variations extending over distances of 2λ perpendicularly to the applied field, where λ is the magnetic penetration depth. These flux lines interact with inhomogeneities inside the superconducting material, leading to a plethora of well-known pinning mechanisms. Furthermore, the static and dynamic response of individual vortices can also be modified if their stray field outside the superconducting volume is altered. This is precisely the reason why multilayered hybrid systems combining superconducting and non-superconducting materials have been an active field of research in the last decade.It has been shown, for instance, that the stray field of an isolated moving vortex can induce eddy currents in a nearby metallic layer, leading to a velocity dependent damping force 1,2 . This effect can be exploited to provide better stability and quench protection in superconducting cables by reducing the speed of flux jumps 3,4 . More spectacular is the possible use of the monopolar magnetic field emanating from a vortex as a submicron-sized magnetic tweezers to locally polarize spin carriers in a diluted magnetic semiconductor 5 . Among these hybrid devices, the heterostructures combining superconductivity and magnetism, two antagonistic quantum macroscopic states, arguably represent the most investigated systems so far [6][7][8][9] . A simple attempt to classify the superconductor (S-layer) -ferromagnet (F-layer) hybrids, where the F-layer and the S-layer are in close proximity and interact only through their stray fields, consists of comparing the relative field strength scales of each subsystem. Indeed, if the coercive field, H coe , of the ferromag...

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