Correlation between doping induced disorder and superconducting properties in carbohydrate doped MgB2

TL;DR

This study investigates how carbohydrate doping affects the disorder and superconducting properties of MgB2, revealing that lower sintering temperatures increase disorder and influence critical current density and transition temperature.

Contribution

It provides a detailed correlation between doping-induced disorder, lattice strain, and superconducting properties, introducing a percolation model to explain high-field critical current enhancements.

Findings

Lower sintering temperature increases carbon substitution and lattice disorder.

Disorder correlates with transition temperature and resistivity.

Enhanced high-field critical current density is explained by a percolation model.

Abstract

A comprehensive study of the effects of carbohydrate doping on the superconductivity of MgB2 has been conducted. In accordance with the dual reaction model, more carbon substitution is achieved at lower sintering temperature. As the sintering temperature is lowered, lattice disorder is increased. Disorder is an important factor determining the transition temperature for the samples studied in this work, as evidenced from the correlations among the lattice strain, the resistivity and the transition temperature. It is further shown that the increased critical current density in the high field region can be understood by a recently-proposed percolation model [Phys. Rev. Lett. 90 (2003) 247002]. For the critical current density analysis, the upper critical field is estimated from a correlation that has been reported in a recent review article [Supercond. Sci. Technol. 20 (2007) R47], where a sharp increase in the upper critical field by doping is mainly due to an increase in lattice disorder or impurity scattering. On the other hand, it is shown that the observed reduction in self-field critical current density is related to the reduction in the pinning force density by carbohydrate doping.