Thermal Fluctuations in YBCO Thin Film on MgO Substrate

The c-axis orientation YBa2Cu3O thin lm was prepared directly on MgO substrate by the pulse laser deposition. The thickness of the lm was 170 nm. The superconducting critical temperature was T c50% = 89 K and the width of superconducting transition was T = 1.6 K. Temperature dependence of the critical current of the lm was obtained from the temperature dependences of the imaginary part of the AC susceptibility using the Bean model. The critical current density was Jc = 1.2 10 7 A/cm 2 at 77 K in the self eld. The critical exponents were calculated for several values of the DC applied magnetic eld using the temperature dependences of magnetoresistivity. The thermal uctuations in vicinity of the critical temperature were analysed.