Modelling of the magnetic behaviour of random granular superconductorsby the single junction model

Abstract

The magnetic measurements of the Josephson critical field andintergranular critical currents are presented for the Bi2223 compound. Theinvestigations prove that the Josephson critical field value is mainlydependent on the intergranular critical current density. The other factorslike the grain dimensions and shapes, sample porosity and density are lessimportant. The relation between the Josephson critical field and critical currentHcJ(Jc) is well described within the single junction model,Hcj∝JcλJ. The temperaturedependence of HcJ can also be well fitted according to the single junctionmodel with a critical current dependence, Jc∝(1-T/TcJ)α. The critical currentdensity versus temperature is almost linear indicating the presence ofsuperconductor-insulator-superconductor (SIS)type junctions.