Hydrostatic Pressure Effect on the Superconducting Transition Temperature of MgB2

The pressure effect on the superconducting transition temperature of MgB2 has been determined using gas pressure up to 1 GPa. The transition temperature Tc was found to decrease linearly at a constant rate over the whole pressure range. The recently observed dramatic decrease of dTc/dp at the 40 K freezing pressure (0.5 GPa) cannot be confirmed. The pressure coefficient was also found to be independent of the hydrostatic or nonhydrostatic He environment. The differences in recently reported values of dTc/dp may be attributed to variations in the sample conditions, e.g. stoichiometry.