Direct observation of nanometer-scale pinning sites in (Nd_0.33Eu_0.20Gd_0.47)Ba₂Cu₃O single crystals

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

Corresponding author: Pintu.Das@cpfs.mpg.de

Received: 19 March 2008
Accepted: 12 June 2008

Abstract

We report on the observation of self-organized stripe-like structures on the as-grown surface and in the bulk of (Nd,Eu,Gd)Ba₂Cu₃O_y single crystals. The periodicity of the stripes on the surface lies between 500800 nm. These are possibly the growth steps of the crystal. Transmission electron microscopy investigations revealed stripes of periodicity in the range of 2040 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.