Universal relationship between crystallinity and irreversibility field of MgB2

TL;DR

This study reveals a universal correlation between crystallinity, measured by FWHM of the MgB2 (110) peak, and the irreversibility field Hirr, across various MgB2 forms, highlighting the role of crystallinity in superconducting properties.

Contribution

It uncovers a universal relationship between crystallinity and Hirr in MgB2, including carbon-doped samples, linking structural distortion to magnetic performance.

Findings

Hirr increases with FWHM of MgB2 (110) peak.

Samples with larger FWHM show enhanced Jc under high magnetic fields.

Crystallinity explains variations in Hirr across MgB2 forms.

Abstract

The relationship between irreversibility field, Hirr, and crystallinity of MgB2 bulks including carbon substituted samples was studied. The Hirr was found to increase with an increase of FWHM of MgB2 (110) peak, which corresponds to distortion of honeycomb boron sheet, and their universal correlation was discovered even including carbon substituted samples. Excellent Jc characteristics under high magnetic fields were observed in samples with large FWHM of (110) due to the enhanced intraband scattering and strengthened grain boundary flux pinning. The relationship between crystallinity and Hirr can explain the large variation of Hirr for MgB2 bulks, tapes, single crystals and thin films.