In-plane anisotropy of the critical current and remanent magnetization in the twin-free BYa_2Cu_3O_(7- delta ) single crystals

摘要

We show the existence of significant anisotropy of the critical current within the ab-plane in the field range of the fishtail effect and irreversibility line. The in-plane anisotropy leads to the double-peak structure of the fishtailed magnetization. We observed this feature only in the untwinned crystals and explained the splitting of the fishtail by a separation of the field positions of the second peak (H_(peak)) for the local critical current densities along a (j_a) and b(j_b) axes. In contrast, the in-plane critical current anisotropy at zero-field is very small. The remanent magnetization M_(rem) measured after turning off the applied field from H_(peak) to 0 is strongly different from M_(ZFC), in spite of negligibe M_(FC) ( approx approx 0). We explain the difference of M_(rem) from M_(FC)-M_(ZFC) by the field-induced anisotropic pinning.