McElfresh M, Miller TG, Schaefer DM, Reifenberger R, Muenchausen RE, Hawley M, Foltyn SR, and Wu XD.
Dept. of Phys. Purdue Univ., West Lafayette, IN, USA.
Correlation of surface topography and flux pinning in superconducting YBaCuO films.
Journal of Applied Physics, vol.71, no.10, 15 May 1992, pp.5099-102. USA.
The surface topography of YBa/sub 2/Cu/sub 3/O/sub 7/ thin films prepared by pulsed laser deposition is studied by atomic force microscopy and scanning tunneling microscopy. The possible contributions from observed structural features to the critical current density J/sub c/ are discussed. It is shown that the contribution of the screw dislocations associated with some structures can be either repulsive or attractive, depending on the dominant pinning mechanism. At low magnetic fields (to about 0.26 kOe) these dislocations can account for the observed critical current density values (J/sub c/>10/sup 11/ A/m/sup 2/) while for larger fields the higher-density steplike growth structures can account for significant values of J/sub c/. It is shown that the pinning strength associated with pinning at steps varies inversely with thickness. (26 References).