Theoretically as well as experimentally there are still open questions related to nanoscale superconductivity and its interaction with (ferro-)magnetism. Nuclear resonant scattering (NRS) and nuclear inelastic scattering (NIS) of synchrotron radiation prove to be unique techniques able to probe the local environment of the atoms. In order to show the strength of both techniques, we present two different cases.
In superconductivity, it is known that phonons play a central role. In decreasing the size of a superconductor, the phonon density of states (PDOS) can be modified, thus can influence the electron-phonon coupling. We aimed at resolving the PDOS of Nb3Sn thin film with NIS and calculated the influence of phonons on the decrease of the critical temperature in thin films.
In a second case, we turned our attention to the influence of superconductivity on magnetism. The interplay between magnetism and superconductivity is an important research field both from theoretical and experimental point of view. These hybrid systems show remarkable variations of their superconducting as well as magnetic behavior, e.g. proximity-induced magnetism , vortex pinning, ratchet motion etc. However, in most cases the magnetic material does not undergo major changes upon going through the superconducting phase transition, despite the fact that they mutually interact. In proper conditions, i.e. when the energy for magnetic ordering and pairing energy of the superconductor are comparable, the superconductor should become strong enough to influence the properties of the magnetic material significantly. In order to achieve this conditions we studied Fe nano islands covered with a superconducting Nb thin film via NRS. The technique allowed a precise observation of the orientation of the Fe magnetic moments above and below the critical temperature.
1Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium