Percolation effects in composites superconductor - ferromagnetic half - metal

摘要

We investigated transport characteristics of composite that consist of the superconductor MgB_2 and ferromagnetic half-metallic nanoparticles La_(0.7)Ca_(0.3)MnO_3 (LCMO). The experiments were carried out in a wide temperature range with different volume content of the magnetic impurity. It was found that over 25% of the impurity manganite breaches percolation paths of the diboride magnesium. This leads to a considerable broadening of the MgB_2 superconducting transition and the formation of the network of contacts through the ferromagnetic inclusions. This result shows the possibility of the spin - activated surface realization on the superconductor -manganite boundary. It's allowing the free transition of Cooper pairs with s - wave symmetry of the order parameter in a ferromagnet with 100% spin-polarized carriers.