Atomic force microscopy and scanning tunnelling microscopy scans of SmBa2Cu3Ox (Sm123) high-Tc superconductors (single crystals and melt-textured samples) prepared using different growth techniques revealed the presence of nanoscale stripe-like structures, which are found to be sometimes parallel over several micrometres and sometimes wavy. These structures consist of chemical compositional fluctuations inherent to the light rare earth high-Tc superconductors and may act as effective pinning centres due to their periodicity of typically 10-60nm which is comparable to the ideal pinning centre size 2ξ (∼10nm for YBa2Cu3Ox in the ab-plane). Nanostripes are observed in Sm123 single crystals grown by the top-seed pulling technique and in melt-textured samples. The periodicity of the nanostripes is found to be much larger (∼50nm) in the former samples than in the melt-textured samples (10-25nm). Detailed measurements reveal that the nanostripes are formed by chains of individual nanoclusters formed from unit cells of the Sm-rich phase, Sm1+xBa2-xCu3Oy. The control of these pinning structures running throughout the whole sample volume may be a key to improving critical current densities, especially at high external magnetic fields.
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