Magnetization studies on superconducting MgB₂ - lower and upper critical fields and critical current density

Magnetization studies have been carried out on superconducting MgB$_2$ (T$_c$=37K) in the temperature range of 2-50K and in magnetic field up to 5 Tesla. From these measurements, values of the lower critical field H$_c1$(0), upper critical field H$_c2$(0) at zero K are estimated to be ~300 Oe and ~12.5 Tesla, respectively, which yield a value of ~26 for the Ginzburg-Landau parameter, k. Magnetization hysteresis loops have been obtained at various temperatures from which the magnetization critical current density is estimated using Bean's critical state model.