Relationship between surface resistance and critical current density of HTS thin films in a DC magnetic field

We investigated the relationship between the surface resistance (R/sub s/) and critical current density (J/sub c/) of DyBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (DyBCO) thin films in a dc magnetic field. The R/sub s/ of DyBCO films at 21.8 GHz was measured using a dielectric resonator method and the J/sub c/ was determined by magnetic measurement and Bean's model. A dc magnetic field of up to 5 T was applied along the c-axis of the films. The relationship between the R/sub s/ and J/sub c/ of DyBCO thin films under a zero magnetic field was explained by the following equation, R/sub s/=/spl alpha//spl times/10/sup 7//J/sub c/, where /spl alpha/ is a constant of 1.2, and the units of the R/sub s/ and J/sub c/ are ohm and A/m/sup 2/, respectively. In addition, the R/sub s/ in dc magnetic fields up to 5 T were inversely proportional to the J/sub c/. However, the parameter /spl alpha/, which was fitted from the R/sub s/-J/sub c/ characteristics in each magnetic field, increased slightly with an increase the magnitude of the applied field. These results indicate that the relationship between the R/sub s/ and J/sub c/ in a zero magnetic field may be a general property of HTS thin films and that the /spl alpha/ in DyBCO thin films depends on the magnitude of the applied magnetic field.