Microwave heating-induced DC magnetic flux penetration in YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ superconducting thin films

摘要

The magneto-optical imaging technique is used to visualize the penetration ofthe magnetic induction in YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin films duringsurface resistance measurements. The in-situ surface resistance measurementswere performed at 7 GHz using the dielectric resonator method. When only themicrowave magnetic field $H_{rf}$ is applied to the superconductor, no$H_{rf}$-induced vortex penetration is observed, even at high rf power. Incontrast, in the presence of a constant magnetic field superimposed on $H_{rf}$we observe a progression of the flux front as $H_{rf}$ is increased. A localthermometry method based on the measurement of the resonant frequency of thedielectric resonator placed on the YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ thin filmshows that the $H_{rf}$--induced flux penetration is due to the increase of thefilm temperature.