Intrinsic Surface Resistance of YBCO Thin Films Under DC Magnetic Field

Abstract

We investigated the dc magnetic field and temperature dependences of the microwave intrinsic surface resistance (Rsint) of YBa2Cu3Oy (YBCO) superconducting thin films with various thicknesses. We used YBCO films from 100, 200, and 300 nm thick YBCO films deposited on CeO2/Al2O3 substrates. The Rsint is means the surface resistance of YBCO film without the dielectric loss of the substrates. The Rsint was obtained from measured surface resistance (Rs) by using a phenomenological equation. The Rs was measured using the dielectric resonator method at 21.8 GHz. A dc magnetic field of up to 5.0 T was applied parallel to the c-axis of the superconducting thin films during the Rs measurements. The Rsint of the YBCO thin films increased when the dc magnetic field was applied. These relations could be explained with the two-fluid model for high-frequency and high-magnetic field limits. The Rsint ratio (defined as Rsint (5T)/Rsint (0T)) slightly decreased with the film thickness. These results indicate that the Rsint of HTS films depends on the film thickness in the dc magnetic field and the Rsint in a dc magnetic field may be related to the pinning center in the HTS films.