Volume 83, Number 3, August 2008
Article Number 37005
Number of page(s) 4
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 17 July 2008
EPL, 83 (2008) 37005
DOI: 10.1209/0295-5075/83/37005

Direct observation of nanometer-scale pinning sites in (Nd0.33Eu0.20Gd0.47)Ba2Cu3O$_{7-\delta}$ single crystals

P. Das1, M. R. Koblischka1, S. Turner2, G. van Tendeloo2, Th. Wolf3, M. Jirsa4 and U. Hartmann1

1  Institute of Experimental Physics, Saarland University - D-66041 Saarbruecken, Germany, EU
2  EMAT Research Group, University of Antwerp - Groeneborgerlaan 171, B-2020 Antwerpen, Belgium, EU
3  Forschungszentrum Karlsruhe GmbH, Institute of Solid State Physics - D-76021 Karlsruhe, Germany, EU
4  Institute of Physics ASCR - Na Slovance 2, CZ-182 21 Prague 8, Czech Republic, EU

received 19 March 2008; accepted in final form 12 June 2008; published August 2008
published online 17 July 2008

We report on the observation of self-organized stripe-like structures on the as-grown surface and in the bulk of (Nd,Eu,Gd)Ba2Cu3Oy single crystals. The periodicity of the stripes on the surface lies between 500$\hbox{--}$800 nm. These are possibly the growth steps of the crystal. Transmission electron microscopy investigations revealed stripes of periodicity in the range of 20$\hbox{--}$40 nm in the bulk. From electron back scattered diffraction investigations, no crystallographic misorientation due to the nanostripes has been found. Scanning tunneling spectroscopic experiments revealed nonsuperconducting regions, running along twin directions, which presumably constitute strong pinning sites.

74.25.Qt - Vortex lattices, flux pinning, flux creep.
74.25.Sv - Critical currents.
74.62.Dh - Effects of crystal defects, doping and substitution.

© EPLA 2008