Study of superconducting properties of MgB2

الأصل · EN

We synthesized single crystalline and policrystalline MgB₂ under ambient pressures. The single crystals of MgB₂ were of good quality, where the crystal structure refinements were successfully converged with R = 0.020. The specific heat of policrystalline MgB₂ samples has been measured in a temperature range between 2 and 60 K in magnetic field up to 6 T. The measurement gave the coefficient of the linear term in the electronic specific heat, gamma = 3.51 mJ/K² mol, and the jump of the specific heat, 2.8 mJ/K² mol at 38.5 K. It is shown from the analysis of the specific heat that the electronic specific heat in the superconducting state differs largely from the conventional BCS weak coupling theory. From the results of measurements of the magnetic properties on single crystal samples, we found a sharp superconducting transition at 38 K with transition width Delta Tc = 0.8 K and the superconducting anisotropy ratio gamma increasing from about 1 near Tc to 4.0 at 25 K.