We characterized ordered compositional fluctuation in high-quality SmBa2Cu3O7-δ, (Sm0.5Eu 0.5)Ba2Cu3O7-δ, and (Sm 0.33Eu0.33Gd0.33)Ba2Cu 3O7-δ superconductors by atomic force microscopy, scanning tunnelling microscopy, and transmission electron microscopy. The presence of nanostripes along the crystalline c direction was confirmed in SmBa2Cu3O7-δ single crystals and in melt-processed (Sm0.5Eu0.5)Ba2Cu 3O7-δ, (Sm0.33Eu0.33Gd 0.33)Ba2Cu3O7-δ materials. Meanwhile, thickness fringes originating from the twin boundaries were also identified in some samples; these could be clearly separated from real nanostripes with sample tilting. Compositional nanostripes displayed spatial variation in both shape and wavelength over a large area of RE-Ba-Cu-O single domains. The origin of the nanostripe is discussed in the context of the competitive growth mechanism of RE1+xBa2-xCu 3O7-δ solid solution.
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