Superconducting properties of MgB2 bulk materials prepared by high-pressure sintering

Abstract

High-density bulk materials of a recently discovered 40 K intermetallic ${\mathrm{MgB}}_{\mathrm{2}}$ superconductor were prepared by high-pressure sintering. Superconducting transition with the onset temperature of 39 K was confirmed by both magnetic and resistive measurements. Magnetization versus field $\mathrm{(M–H)}$ curve shows the behavior of a typical type-II superconductor and the lower critical field $H_{\text{c1}}\text{(0)}$ estimated from the $\mathrm{M–H}$ curve is 0.032 T. The bulk sample shows good connection between grains and critical current density $J_c$ estimated from the magnetization hysteresis using sample size was ${\text{5×10}}^4 {\mathrm{A/cm}}^{\mathrm{2}}$ at 20 K and 1 T. Upper critical field $H_{\text{c2}}\text{(0)}$ determined by extrapolating the onset of resistive transition and assuming a dirty limit is 18 T.