Origin of l / f noise peaks of YBa 2 Cu 30 x films in a magnetic field
نویسنده
چکیده
The temperature and magnetic field dependence of llfnoise has been measured in epitaxial YBa2Cu30, films. In a magnetic field, two noise pealcs were observed as temperature decreases; one at higher temperature was found to match the thermal fluctuation of the sample resistance and the other near the foot of the transition was found to be magnetic-field dependent. The location of the latter was shifted toward low temperature and the peak height was decreased as a magnetic field increased. In a zero field only one peak from the resistance fluctuation was observed. We show that the field-dependent noises are due to flux motion interacting with the pinning potential. A classical model is used to explain the field-induced noise peaks. We interpret that the temperature dependences of the flux bundle size and the sample resistance are the reasons for the noise peaks, and a rough estimation of the temperature and field dependence of the flux bundle size is presented. Any possible relationship between the noise peaks and the flux-line-lattice phase transition is also discussed PACS number: 74.40.+k
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