(1) Tata Institute of Fundamental Research, Homi Bhabha Road, 400 005 Mumbai, India;(2) Department of Physics, Institute of Science, 400 032 Mumbai, India;(3) Aruna Asaf Ali Marg, Nuclear Science Centre, 110 067 New Delhi, India
Abstract:
The vortex dynamics at microwave frequencies in YBa2Cu3O7-δ (YBCO) films have been studied. We observe a peak in the microwave (4.88 and 9.55 GHz) surface resistance in some films in magnetic fields up to 0.8 T. This is associated with the ‘peak-effect’ phenomenon and reflects the order-disorder transformation of the flux line lattice near the transition temperature. Introduction of artificial pinning centers like columnar defects created as a result of irradiation with 200 MeV Ag ion (at a fluence of 4×1010 ions/cm2) leads to the suppression of the peak in films previously exhibiting ‘peak effect’.