Modulation of superconductivity by a magnetic template in Nb/BaFe12O19 hybrids

Inhomogeneous magnetic fields generated by the BaFe12O19 ferromagnetic substrate create a magnetic template for superconducting condensate in the Nb/BaFe12O19 hybrids. Depending on the field and temperature, the magnetic template guides superconductivity to nucleate in different areas: above the magnetic domain walls of the BaFe12O19 forming the domain-wall superconductivity (DWS), above the reversed magnetic domains (RDS), and above the positive magnetic domains forming bulk superconductivity. The DWS, behaving as a superconducting wire network, survives in a broad field range. The RDS, existing in the form of isolated superconducting islands near the saturation field H-s of BaFe12O19, can be described as a two-dimensional two-component random conductor mixture. Being related to the hysteretic domain evolution, superconducting condensate above the reversed domains shows pronounced switching behavior.