Physical property characterization of Fe-tube encapsulated and vacuum annealed bulk MgB2

TL;DR

This study characterizes the physical properties of MgB2 bulk samples prepared via Fe-tube encapsulation and vacuum annealing, revealing their superconducting transition, critical current density, and magnetic behavior.

Contribution

It provides detailed magnetic and resistivity measurements of MgB2 prepared with a novel encapsulation and annealing method, highlighting its superconducting properties and magnetic effects.

Findings

Superconducting transition at 39 K with a sharp diamagnetic signal.

Stable critical current density of ~2.4 x 10^5 A/cm^2 up to 2 T.

Upper critical field of 8 T at 21 K and observation of paramagnetic Meissner effect.

Abstract

We report phase formation, and detailed study of magnetization and resistivity under magnetic field of MgB2 polycrystalline bulk samples prepared by Fe-tube encapsulated and vacuum (10-5 torr) annealed (750 0C) route. Zero-field-cooled magnetic susceptibility (cZFC) measurements exhibited sharp transition to superconducting state with a sizeable diamagnetic signal at 39 K (Tc). The measured magnetization loops of the samples, despite the presence of flux jumps, exhibited a stable current density (Jc) of around 2.4 x 105 A/cm2 in up to 2 T (Tesla) field and at temperatures (T) up to 10 K. The upper critical field is estimated from resistivity measurements in various fields and shows a typical value of 8 T at 21 K. Further, cFC measurements at an applied field of 0.1 T reveal paramagnetic Meissner effect (PME) that is briefly discussed.