Evidence for a directed δt_c-type flux pinning by means of nanostripes in (Sm_0.33Eu_0.33Gd_0.33)Ba ₂Cu₃O_y high-T_c superconductors

By means of four-point transport measurements on bulk, high-T_c superconducting samples of composition (Sm_0.33Eu _0.33Gd_0.33)Ba₂Cu₃O_y exhibiting self-organized nanostripes formed by nanoclusters of the light-rare-earth-rich phase, we find that at temperatures close to the transition temperature the currents flowing parallel to the nanostripes are clearly larger than in the perpendicular direction. Constructing a pinning force diagram from the j_c(H_a)-data obtained, we find strong evidence for a dominating δT_c-pinning when the currents are flowing parallel to the nanostripes.