Improvement of current density by texture and Ic anisotropy in thin filament MgB2/Fe tapes

Thin filament MgB2/Fe tapes have been made by the powder-in-tube technique using a precursor powder prepared by mechanical alloying and deformed by two-axial rolling. Increasing critical current density (Jc) in a parallel external magnetic field has been measured for a reduced filament thickness up to 18.5 µm; this could be effective for future practical fine-filamentary MgB2 conductors. This increase in Jc is attributed to an apparent improvement in texture introduced by rolling. Further increase in Jc with reduction of filament size is limited due to chemical reaction at the filament/Fe interface during the final heat treatment at 600 °C for 3 h. On the other hand, improved texture leads to a strong critical current anisotropy, which increases with the reduced filament thickness and temperature. High Ic anisotropy can lead to an apparent reduction of the total magnet current due to the effect of the radial field component, as in the case of high temperature superconducting coils.

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