Single-core MgB2 tape was made by using the powder-in-tube method, with commercial MgB2 powder and 2-axis rolling deformation in an Fe/Cu sheath. The transport currents were measured at 4.2 to 15K, parallel and perpendicular to external magnetic fields of 0 to 5.5T, or in a constant field of 1T of variable orientation (0 to 180°) to the tape surface. The transport current anisotropy of the tape with different orientations of the tape surface with respect to the external magnetic field was measured, revealing higher currents for a perpendicular field orientation. An IC anisotropy of MgB2/Fe/Cu tape was observed only in low external fields (0 to 2.5T). This behavior was explained by Fe sheath magnetization and was confirmed by the isotropic behavior of MgB2/Cu tape prepared using a similar powder-in-tube process, and by hysteretic IC(B) curves measured in increased and decreased external fields in MgB2/Fe/Cu. The presence of the ferromagnetic barrier in MgB2 composite wire influenced the IC(B) characteristics and was expected to lead to increased hysteretic losses in possible future alternating-current applications.

IC Anisotropy and IC Hysteresis in MgB2/Fe/Cu Tape. P.Kovác, K.Hense, T.Melišek, I.Hušek, H.Kirchmayr: Superconductor Science and Technology, 2002, 15, 1037-9