FIZIKA A 15 (2006) 1 , 17-24

SUPERCONDUCTING PROPERTIES OF THERMALLY-RELAXED Zr₈₀Co₂₀ METALLIC GLASS

IVAN KOKANOVIĆ^a, BORAN LEONTIĆ^a and JAGODA LUKATELA^b

^aDepartment of Physics, Faculty of Science, University of Zagreb, P.O. Box 331,Zagreb, Croatia
^bInstitute of Physics, P.O. Box 304, Zagreb, Croatia

Dedicated to the memory of Professor Zvonko Ogorelec

Received 21 September 2004;   Accepted 16 May 2005
Online 10 November 2006

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 T_c. Experimental values for the crystallisation temperature and activation energy of the crystallisation processes were derived by studying these processes at different heating rates. The T_c 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 other thermally relaxed samples T_c 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 homogeneous on a spatial scale of less than the zero-temperature coherence length x₀.

PACS numbers: 61.42.+h, 74.70.Mq
UDC 537.312

Keywords: Zr₈₀Co₂₀ metallic glass, thermal relaxation, superconductivity, transition temperature T_c, homogeneity, crystallisation exotherm, electrical resistance

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