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Superconducting properties of thermally-relaxed Zr_80Co_20 metallic glass

We have studied the effect of thermal-relaxation on the superconducting properties of Zr80Co20 metallic glass by means of differential scanning calorimetry and electrical resistivity measurements in the vicinity of the superconducting transition temperature Tc. Experimental values for the crystallisation temperature and activation energy of the crystallisation processes were derived by studying these processes at different heating rates. The Tc of the Zr80Co20 metallic glass thermally relaxed with a heating rate of 60 K/min to slightly below its first crystallisation exotherm is higher than in unrelaxed Zr80Co20 metallic glass, whereas in all the other thermally relaxed samples Tc decreases with decreasing heating rates and increasing temperature of relaxation. The homogeneity of the thermally relaxed Zr80Co20 metallic glass is discussed by using the superconducting transition width as a criterion. The superconducting transitions of thermally relaxed Zr80Co20 metallic glass samples are characterised by a sharp fall in electrical resistance. This suggests that the samples are homogenous on a spatial scale of less than the zero-temperature coherence length.

metallic glass ; thermal stability ; crystallisation ; superconductivity

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