Coexistence of ferromagnetism and superconductivity in Ni/Bi bilayers

Phys Rev Lett. 2005 Jan 28;94(3):037006. doi: 10.1103/PhysRevLett.94.037006. Epub 2005 Jan 26.

Abstract

In spite of a lack of superconductivity in bulk crystalline Bi, thin film Bi deposited on thin Ni underlayers are strong-coupled superconductors below approximately 4 K. We unambiguously demonstrate that by tuning the Ni thickness the competition between ferromagnetism and superconductivity in the Ni/Bi can be tailored. For a narrow range of Ni thicknesses, the coexistence of both a superconducting energy gap and conduction electron spin polarization are visible within the Ni side of the Ni/Bi bilayers, independent of any particular theoretical model. We believe that this represents one of the clearest observations of superconductivity and ferromagnetism coexisting.