Magnetization of grain-aligned HoBa2Cu3O7 - δ

This paper reports cylinders of grain-aligned HoBa2Cu3O7-gd superconductors in epoxy investigated using differential magnetization and ac susceptibility techniques int he temperature range 2 K (lte) T (lte) Tc. From both experimental techniques, demagnetizing factors of the grains could be deduced for H(double fence rule)c and for H(double fence rule)a,b, which compare reasonably well with estimates based on the size and shape of the grains. With this information, absolute values of the lower critical field Hc1 (first flux penetration field), its anisotropy and temperature dependence were obtained. Furthermore, magnetization critical current densities (intragrain jc's) were calculated from the magnetization curves as well as from minor hysteresis loops. Pronounced anisotropies of jc as well as significant contributions of the Ho-moments to the magnetization, in particular in the (a,b)-plane, have been observed