Electrical transport properties of a superconductor-ferrimagnet composite in applied magnetic fields

Electrical transport properties of the YBa₂Cu₃O_7-δ + Sr₂FeMoO_6-δ superconductor-ferrimagnet composite as a function of the temperature and applied magnetic field are reported. Four different intervals in the temperature dependence of the resistivity have been found between room temperature and 4.2 K. In the temperature range from 300 K down to T_c¹a semiconducting behavior is observed, whereas below T_c¹the first transition into a superconducting state sets in. Upon further cooling down, the semiconducting behavior appears again below T_minc¹ and then a second superconducting transition starts at T_c²min continuing down to 4.2 K. The magnetoresistance is negative above T_c¹ and positive below it, achieving at 5 K and a field of 10 T a huge value of ∝5700%. We discuss the role of the weak links between the YBa₂Cu₃O_7-δ grains represented by the Sr₂FeMoO_6-δ interlayers on the magnetotransport in the composite. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)