Fabrication of MgB2 tapes sheathed with carbon steels by ex situ and in situ methods

MgB₂ tapes sheathed with carbon steel (CS) were fabricated by a powder-in-tube technique with ex situ and in situ methods. The critical current density (J_c) value of the former tape was about 2 kA/cm² at 4.2 K and 10 T by heat treatment at 900°C, whereas the J_c value of the latter tape reached about 3 kA/cm² by heat treatment at temperature as low as 600°C. The J_c anisotropy with respect to field direction of the tapes fabricated by the ex situ method was much larger than that of the tapes fabricated by the in situ method.