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

We report the phase formation, and present a detailed study of magnetization and resistivity under magnetic field of MgB2 polycrystalline bulk samples prepared by the Fe-tube encapsulated and vacuum (10−5 Torr) annealed (750 ∘C) route. Zero-field-cooled magnetic susceptibility (χZFC) measurements exhibited a sharp transition to the superconducting state with a sizeable diamagnetic signal at 39 K (Tc)(Tc). The measured magnetization loops of the samples, despite the presence of flux jumps, exhibited a stable current density (Jc)(Jc) of around 2.4×105 A/cm2 in up to 2 T (Tesla) field and at temperatures (T)(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, χFC measurements at an applied field of 0.1 T reveal a paramagnetic Meissner effect (PME) that is briefly discussed.