Correlated vortex pinning in Si-nanoparticle doped MgB2

TL;DR

This study investigates how Si-nanoparticle doping affects vortex pinning and magnetic properties in MgB2 superconducting tapes, revealing correlated disorder effects similar to high-temperature superconductors.

Contribution

It provides the first detailed analysis of correlated vortex pinning due to nanoparticle-induced defects in MgB2, highlighting the impact on irreversibility line behavior.

Findings

Doped MgB2 shows a kink in the irreversibility line near 0.3 T.

Nanoprecipitates act as correlated disorder affecting vortex pinning.

Critical current density behavior differs significantly between doped and undoped samples.

Abstract

The magnetoresistivity and critical current density of well characterized Si-nanoparticle doped and undoped Cu-sheathed MgB$_{2}$ tapes have been measured at temperatures $T\geq 28$ K in magnetic fields $B\leq 0.9$ T. The irreversibility line $B_{irr}(T)$ for doped tape shows a stepwise variation with a kink around 0.3 T. Such $B_{irr}(T)$ variation is typical for high-temperature superconductors with columnar defects (a kink occurs near the matching field $% B_{\phi}$) and is very different from a smooth $B_{irr}(T)$ variation in undoped MgB$_{2}$ samples. The microstructure studies of nanoparticle doped MgB$_{2}$ samples show uniformly dispersed nanoprecipitates, which probably act as a correlated disorder. The observed difference between the field variations of the critical current density and pinning force density of the doped and undoped tape supports the above findings.