Nanostructured hybrids of superconductors and ferromagnets

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We propose studying the electronic and magnetic properties of nano-structured hybrid systems consisting of different combinations of ferromagnets and superconductors. Our main goal is to understand the basic mechanism of the interaction between the two competing orders of super-conductivity and ferromagnetism, and thereby elucidate the pairing mechanism of the cuprate high temperature superconductors (HTS). We shall also attempt to control the hybrid systems properties, and check whether they could be utilized in practical applications. For this we shall study the basic properties of bilayers, multilayers and nano-composites consisting of ferromagnets and super-conductors as well as the differently doped HTS. Typical materials that will be used include conventional superconductors such as Al, Pb, Zn and Nb, the HTS cuprates YBa2Cu3O7_s(YBCO), La2_xSrxCuO4 (LSCO), La2_xBaxCuO4 (LBCO), and Bi2Sr2CaCu2O8+5 (BSCCO),and the ferromagnets SrRuO3 (SRO), Nd^Sr^MnOj, Ni, Fe and Fe3O4 (magnetite) nanoparticles. We plan to investigate proximity and interface effects, spintronics phenomena, vortex matter, the pseudogap and the origin of the HTS phase diagram, as well as the interplay between superconductivity and magnetism in artificial nanostructured multilayers in comparison with the intrinsic magneto-superconductors. Nanometer thick films, bilayers and multilayers will be prepared by laser ablation deposition and sputtering. Various experimental techniques will be employed in our studies including scanning tunneling microscopy and spectroscopy (STM and STS), magneto-optics, time resolved optical and THz spectroscopy, and high sensitivity transport and magnetic measurements. This combination of local-probe and 'macroscopic’ measurements will provide a comprehensive picture of the nanostructured hybrids at hand. The experimental efforts, backed up by a theoretical study of fundamental properties of HTS as reflected in our measurements, will be carried out by groups in Germany (Konstanz University) and Israel (The Technion, Bar-Ilan University, and the Hebrew University). These four groups have complementary, wellestablished expertise in the necessary material preparation, characterization and research techniques. We expect that the well-balanced combination of overlapping and complementary fields of expertise and interest of our groups will promote a synergetic collaboration and yield new insight into the physics of HTS and their hybrids with ferromagnets.