Low-temperature thermodynamic properties of amorphous sputtered Zr 100-xCux alloys. Effect of structural relaxation

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Abstract
We report on low-temperature specific heat measurements of superconducting amorphous Zr100-xCux (19 ≤ x ≤ 64) alloys prepared by sputtering that we compare to corresponding alloys obtained by fast liquid-quenching technique. Whereas the superconducting transition temperature Tc is very close for these two kinds of amorphous alloys, indicating that it is almost insensitive to the higher degree of structural disorder inherent to sputtering, both the electronic coefficient γ and the lattice β T3 contribution are larger for the sputtered alloys. The common character of an increasing value of γ with the Zr content is considerably enhanced for the sputtered alloys. However, such surprisingly high y values do not lead to any anomalous behaviour for the superconductivity process, as proved by the complete electronic condensation below Tc. All thermodynamic parameters are sensitive to structural relaxation, at variance with the liquid-quenched alloys, whereas the Tc depression is of the same magnitude in both kinds of alloys