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Determination of the temperature dependence of the penetration depth of Nb in Nb/AlO{sub x}/Nb Josephson junctions from a resistive measurement in a magnetic field

Description: The temperature dependence of the penetration depth of Nb films was determined from resistive transitions of Nb/AlO{sub x}/Nb Josephson junctions in a constant magnetic field applied parallel to the junction planes. Distinct resistance peaks were observed as temperature decreases and those peaks were found to appear when the total flux threading the junction equals an integral multiple of the flux quantum. From this condition, the authors have determined the penetration depth at those peak positions. The temperature dependence was well described by the either dirty local limit or the two-fluid model. This method can be useful for highly fluctuating system like high-temperature superconductors.
Date: November 1, 1993
Creator: Kim, D.H.; Gray, K.E.; Hettinger, J.D. & Kang, J.H.
Partner: UNT Libraries Government Documents Department

Origin of 1/f noise peaks of YBa{sub 2}Cu{sub 3}O{sub x} films in a magnetic field

Description: The temperature and magnetic field dependence of 1/f noise has been measured in epitaxial YBa{sub 2}Cu{sub 3}O{sub x} films. In a magnetic field, two noise peaks 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.
Date: February 1, 1994
Creator: Kang, W.N.; Kim, D.H. & Park, J.H.
Partner: UNT Libraries Government Documents Department