The characteristics of the magnetic flux noise in high temperature superconducting thin-films of yttrium-barium-copper-oxide (YBa2Cu3O7) in the vicinity of artificial grain boundaries have been studied by means of a low critical temperature superconducting quantum interference device (SQUID) magnetometer. The measured power spectrum of the flux noise typically shows 1/f-behaviour at low frequencies. This is, in particular, evident near the transition temperature. When measuring the flux noise near an artificial grain boundary we observe in selected samples additional Lorentzian type spectra in narrow temperature ranges indicative for well-defined barriers for flux hopping. Such spectra are not observed when measuring away from the grain boundary. The distinct fluctuators are seen in the 60-80 K interval corresponding to barrier heights of order 0.1-0.4 eV. If present in Josephson junctions patterned across such artificial grain boundaries, they could lead to serious limitations in the junction performance in certain temperature ranges. (C) 2000 Elsevier Science B.V. All rights reserved.
Bukh, K. R., Jacobsen, C. S., Hansen, J. B., Shen, Y. Q., & Holst, T. (2000). Observation of distinct, temperature dependent flux noise near bicrystal grain boundaries in YBa2Cu3O7-x films. Physica C: Superconductivity and its Applications, 333(3-4), 133-138. https://doi.org/10.1016/S0921-4534(00)00232-X