Magneto-optics: Imaging and Quantitative Analysis

The work presented in this thesis deals with the magneto-optical imaging (MOI) technique, which was developed during the PhD course of the candidate, with an equipment at the international state-of-the-art. The quantitative theoretical formalism was critically reproduced and verified, along with a careful calibration procedure. A novel, big improvement was brought for all the MOI experiments, aimed at the quantitative reconstruction of the current density, by an iterative procedure (Supercond. Sci. Technol. 16, 71 (2003)). The new MOI method was then applied to study a wide class of superconducting materials and a thorough study about the electrodynamics of superconducting films was accompanied by a research in the high energy nuclear field for creating suitable nanometric-size defects. In particular: the anisotropic interaction of correlated nanostructures with vortices was verified for the first time (Phys. Rev. B 68, 014507 (2003)); controlled micro-modulations of the superconducting properties through confined high-energy heavy-ion irradiation were achieved and nonlocal electrodynamics plus new vortex matter phases were observed; the measurements of hybrid heterostructures (superconducting/ferromagnetic bi-layers) was joining the studies of macroscopic quantum physics of vortices and of the macroscopic (but localized) spin structures (interacting with vortices indeed), in the ferromagnetic film.