Position-dependent analysis of nanostripes in bulk light-rare-earth superconductors

The light rare-earth based bulk superconductors were found recently to exhibit self-organized nanostripes, especially pronounced in the ternary compound (Nd,Eu,Gd)Ba2Cu3Ox. The nanostripes, consisting of aligned nanoclusters (dimensions 10-50 nm in diameter), are formed during the sample growth, so it is an essential issue for the production of such samples to be able to control the formation of these nanostripes in order to generate effective pinning sites at high magnetic fields. Here, we investigate bulk pellets with a diameter of 18 mm and a height of 10 mm. These pellets are characterized prior to the cutting by means of trapped field measurements. Small samples are cut from the bulk pellet in various growth directions and sample sectors. The nanoscopic investigations are performed using atomic force microscopy and scanning tunneling microscopy in ambient conditions.