Correlative study of Rs and Jc for 123 superconducting thin films

Abstract

We have studied the relationship between the microwave surface resistance,Rs (measured by a dielectric resonator technique at 22 GHz), and the critical current density,Jc (obtainedvia a transport method), for various superconducting thin films belonging to the 123 family. It is foundthat Rs = 4.29 × 107Jc−0.98 for YBa2Cu3Oz(YBCO) films on MgO, which is in good agreement with the reported value(Rs,22 GHz = 1.8 × 107Jc−1) forYBCO on BaSnO3 buffered MgO. On the other hand, we observedRs = 6.8 × 1023Jc−2.55 andRs = 2.2 × 105Jc−0.76, respectively,for Y0.90Ca0.10Ba2Cu3Oz on MgOand Dy0.40Ho0.60Ba2Cu3Oz ((D,H)BCO) on LaAlO3 films, where Rs is in Ω and Jc is inA m−2. The observeddeviation in the Rs–Jc relations (from the simple relation, which holds good for pure YBCO films) for (D, H)BCO filmsmay be attributed to the existing different temperature dependence ofRs for these films. On the other hand, in the case ofY1−xCaxBa2Cu3Oz (YCBCO) films,the very low Jc and the microstructural imperfections are considered a plausible cause for the observeddeviation from the simple relation. Though the pre-exponential factor,m,in Rs = mJc−n is believed to be highly sample dependent, it is inferred from the correlative results (obtainedfrom eight films, i.e., YBCO (two films); (D, H)BCO (three films); YCBCO (three films withx = 0.02, 0.05,0.10)) that m and n in the Rs = mJc−n correlation are related to each other in such a way thatlog(m) varies linearlywith n. Anm value of the orderof 107 is observedtypically when the n value is 1.