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 Fe₂O₃ nanoparticles embedded into the bulk of MgB₂ superconductor. Nonmagnetic Mo₂O₅ nanoparticles also increase pinning strength, but less than magnetic Fe₂O₃. 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.