Correlation between lattice distortions and flux pinning behavior in benzene-doped Fe-sheathed MgB2 wires

This study investigates the effects of benzene-derived carbon doping on the structural and superconducting properties of Fe-sheathed MgB₂ wires fabricated by the in-situ PIT method. Differential scanning calorimetry showed that benzene addition shifts the MgB₂ formation temperature and reduces reaction enthalpy, indicating modified phase formation. X-ray diffraction confirmed lattice parameter changes due to partial carbon substitution, while EDX revealed locally limited carbon distribution. AC magnetic susceptibility and magnetization measurements demonstrated that doping enhanced the irreversibility field and critical current density, especially at high fields. Dew-Hughes model analysis showed that the flux pinning mechanism shifted from point pinning in the pure sample to surface pinning in the doped wires. These improvements result from combined lattice distortions and phase effects caused by the aromatic carbon source. The findings highlight benzene as an effective carbon dopant for tailoring flux pinning behavior and improving the high-field performance of MgB₂ superconductors, despite potential carbon inhomogeneity.