Superconducting properties of MgB2 prepared by high and ambient pressures

The new superconductor MgB2 has been prepared in two ways, by high pressure and ambient pressure synthesis. The superconducting properties were measured and compared. It is found that the sample prepared by high pressure is much denser than that prepared under ambient pressure. Accordingly the high pressure sample has a very narrow transition width and a much higher bulk critical current density.