Superconducting nanocomposites: enhancement of bulk pinning and improvement of intergrain coupling

Heterogeneous sonochemical method was applied for synthesis of novel superconducting nanocomposites consisting of magnetic (and/or nonmagnetic) nanoparticles embedded into the bulk of ceramic superconductors . In addition to in-situ production of the efficient pinning centers, this synthesis method considerably improves the interbrain coupling. Significant enhancement of the magnetic irreversibility is reported for Fe/sub 2/O/sub 3/ nanoparticles embedded into the bulk of MgB/sub 2/ superconductor. Nonmagnetic Mo/sub 2/O/sub 5/ nanoparticles also increase pinning strength, but less than magnetic Fe/sub 2/O/sub 3/. Detailed magnetization and electron microscopy characterization is presented. Theory of bulk magnetic pinning due to ferromagnetic nanoparticles of finite size embedded into the superconducting matrix is developed.