Effect of annealing on the superconducting properties of two amorphous alloys: Nb 70 Zr 15 Si 15 and Zr 85 Si 15

A. Inoue, S. Okamoto, Naoki Toyota, T. Fukase, K. Matsuzaki, T. Masumoto

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Abstract

The changes in the superconducting and electronic properties of amorphous Nb 70 Zr 15 Si 15 and Zr 85 Si 15 alloys with annealing were examined with an aim to evaluate the effect of structural relaxation on the superconductivity of metal-metalloid type amorphous alloys. T c rises once from 3.99 to 4.42 K on annealing at temperatures below about 473 K for the Nb-Zr-Si alloy and from 2.71 to 2.75 K at temperatures below about 373 K for the Zr-Si alloy, and with further rising annealing temperature, t d , lowers monotonically to a final relaxed value (≃3.15 K for Nb 70 Zr 15 Si 15 and ≃2.49 K for Zr 85 Si 15 ), which is independent of the previous thermal cycling. These results indicate that the thermal relaxation of an amorphous phase occurs through at least two stages. The lowering of T c occurs exponentially with t d , and an activation energy for the relaxation process and the frequency of jump over the barrier were estimated to be about 2.03 eV and 2.4×10 14 sec -1 for Nb 70 Zr 15 Si 15 and about 1.28 eV and 1.2×10 11 sec -1 for Zr 85 Si 15 , respectively. The high frequencies indicate that the relaxations occur more or less independently of each other in a non-co-operative manner. The dressed density of electronic states at the Fermi level, N(E f ) (1+λ), which was calculated from the measured values of ρ n and (d H c2 dT)T c , exhibited a similar annealing temperature dependence to that of T c . From this the change in T c on thermal relaxation was interpreted as due to the changes in λ and/or N(E f ). From the depressions of J c (H) and fluxoid pinning force on annealing in a temperature range of 473 to 873 K, it was concluded that the structural relaxation from a less homogeneous quenched-in state to a homogeneous stable state occurred on the scale of coherence length (≃7.5 nm) during the annealing.

Original languageEnglish
Pages (from-to)2719-2730
Number of pages12
JournalJournal of Materials Science
Volume19
Issue number8
DOIs
Publication statusPublished - 1984 Aug 1

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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