Critical current anisotropy in non-sintered metal-clad MgB₂ tapes

Ag/MgB₂, Cu/MgB₂ and SS/MgB₂ (stainless) tapes were fabricated by the oxide powder-in-tube method. X-rays diffraction studies showed the formation of moderate c-axis texturing in the MgB₂ core, which increases with the sheath strength and correlates with the core microhardness. Magnetization hysteresis loops of the tapes were measured for applied magnetic field (H) parallel and normal to the tape plane, in a wide range of H (0-5 T) and temperature (5-25 K). The critical current density (J_cm), calculated using the extended Bean model, indicates the possible current limitation due to inter-particle links. Significant anisotropy in J_cm is observed. The "parallel" J_cm is one order of magnitude higher than the "normal" J_cm which is of the same order of magnitude as transport J_c in non-sintered tapes. This anisotropy is assumed to be originated from the weak large-scale connectivity (deformation-induced crack formation) in densified MgB₂ core after the rolling process.