Mossbauer and transport studies of amorphous and icosahedral Zr-Ni-Cu-Ag-Al alloys

• The alloy Zr65Al7.5Ni10Cu7.3Fe0.2Ag10 in the amorphous and icosahedral states, and the bulk amorphous alloy Zr65Al7.5Ni10Cu7.5Ag10, have been studied with Fe-57 Mossbauer spectroscopy, electrical resistance and magnetoresistance techniques. The average quadrupole splitting in both alloys decreases with temperature as T-3/2. The average quadrupole splitting in the icosahedral alloy is the largest ever reported for a metallic system. The lattice vibrations of the Fe atoms in the amorphous and:icosahedral alloys are well described by a simple Debye model, with the characteristic Mossbauer temperatures of 379(29) and 439(28) K, respectively. Amorphous alloys Zr65Al7.5Ni10Cu7.5Ag10 and Zr65Al7.5Ni10Cu7.3Fe0.2Ag10 have been found to be superconducting with the transition temperature, T, of about 1.7 K. The magnitude of T, and the critical field slope at T, are in agreement with previous work on Zr-based amorphous superconductors, while the low-temperature normal state resistivity is-larger than typical results for binary and ternary Zr-based alloys. The resistivity of icosahedral Zr65Al7.5Ni10Cu7.3Fe0.2Ag10 is larger-than that for the amorphous ribbon of the same composition, as inferred both from direct measurements on the ribbons and from the observed magnetoresistance. However the icosahedral sample is non-superconducting in the measurement range down to 1.5 K. The results for the resistivity and the superconducting T-c both suggest a stronger electronic disorder in the icosahedral phase than in the amorphous phase.

Nyckelord

quasi-crystalline phase

u-si alloys

supercooled liquid region

electric-field gradient

bulk metallic-glass

temperature-dependence

noncubic metals

physical-properties

v alloys

pd

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