LOW-FREQUENCY NOISE AND HALL-EFFECT MEASUREMENTS ON YBA2CU3O7-DELTA THIN-FILMS

We report 1/f noise and Hall effect measurements performed on c-axis o riented YBa2Cu3O7-delta thin films at superconducting transition and i n normal state. Magnetic fields up to 6 kG were applied parallel to c- axis. The voltage noise spectral density was normalized using Hall car rier density as well as atomic concentration. Close to the superconduc tive state, normalized voltage noise spectral density had a sharp rise . The noise did not seem to originate from local thermal fluctuations. We interpreted the data in terms of the classic percolation model nea r superconductive transition, according to which normalized noise is p roportional to R(-k'/s), where R is the macroscopic sample resistance and k' and s are critical exponents, The ratio k'/s, which can be rega rded as an index of the rise of normalized noise, steadily increased w ith higher magnetic field. The zero-Gauss value of k'/s was calculated as 1.06; a result that agrees with the prediction of the classical pe rcolation theory for a 2-D network.