By using a highly sensitive homemade AC magnetic susceptibility technique, the magnetic flux penetration has been measured in YBa2Cu3O7 - δ single crystals with giant screw dislocations (having the structure of the Archimedean spirals) exhibiting a = 3 spiral turnings, the pitch b = 18.7 μm and the step height c = 1.2 nm (the last parameter is responsible for creation of extended weak-link structure around the giant defects). The magnetic field applied parallel to the surface enters winding around the weak-link regions of the screw in the form of the so-called spiral Josephson fluxons characterized by the temperature dependent pitch bf(T). For a given temperature, a stabilization of the fluxon structure occurs when bf(T) matches b (meaning an optimal pinning by the screw dislocations) and manifests itself as a pronounced low-field peak in the dependence of the susceptibility on magnetic field (applied normally to the surface) in the form resembling the high-field (Abrikosov) fishtail effect. © Pleiades Publishing, Inc., 2010.
Sergeenkov, S., Cichetto, L., Rivera, V. A. G., Stari, C., Marega, E., Cardoso, C. A., & Araujo-Moreira, F. M. (2010). Pinning of spiral fluxons by giant screw dislocations in YBa<inf>2</inf>Cu<inf>3</inf>O<inf>7 - δ</inf> single crystals: Josephson analog of the fishtail effect. JETP Letters, 30-34. https://doi.org/10.1134/S0021364010010078