Gianluca Ghigo

Nanostructuring superconductors by ion beams: A path towards materials engineering

The paper deals with nanostructuring of superconducting materials by means of swift heavy ion beams. The aim is to modify their structural, optical and electromagnetic properties in a controlled way, to provide possibility of making them functional for specific applications. Results are presented concerning flux pinning effects (implantation of columnar defects with nanosize cross section to enhance critical currents and irreversibility fields), confined flux-flow and vortex guidance, design of devices by locally tailoring the superconducting material properties, analysis of disorder-induced effects in multi-band superconductors. These studies were carried out on different kinds of superconducting samples, from single crystals to thin films, from superconducting oxides to magnesium diboride, to recently discovered iron-based superconductors.

Proton irradiation induced effects on YBCO films analysed by magneto-optics

In this paper we present a quantitative magneto-optical analysis on c-axis oriented YBCO thin films, as grown and irradiated with 3.5 MeV protons at three different fluences. Magneto-optical measurements were performed over the temperature range 5–70 K and at magnetic fields up to 150 mT. The local current density values were obtained from the field maps by means of the Biot-Savart law inversion. The critical current density (Jc) is locally defined as the current density where the maximum pinning efficiency is reached. This procedure allows obtaining Jc independently of dissipation threshold criteria or critical state model. A Jc enhancement emerges for irradiation at the lowest fluence ( Ф +2.5⋅1015 cm−2) in the whole investigate temperature range. On the contrary at increasing the irradiation dose a temperature-dependent crossover from an enhancement to a worsening of Jc is exhibited.