Structural effects on the superconducting and magnetic behavior of aluminum-rich metallic glasses

We have performed specific heat, resistivity, and magnetic measurements on a series of glassy aluminum alloys containing up to 93 at. % Al. In addition to the fact that we can extrapolate from our data the values of superconducting temperature (>5 K) and resistivity (approx.20 ..mu cap omega.. cm) for amorphous Al, our results also provide evidence that significant softening of phonon modes (in the case of glassy Al/sub 92/La/sub 8/, a drastic reduction is observed with a Debye temperature of approx.242 K as compared with approx.428 K in crystalline Al) is responsible for the enhanced superconductivity of up to 8.5 K observed in some metastable Al alloys. For glassy Al alloys containing a few at. % Gd, the maximum in specific heat is observed at more than twice the magnetic ordering temperature defined by the cusp in susceptibility, markedly different from that of canonical spin glasses. The structural differences between these glassy Al alloys and other magnetic alloys are pointed out. Ce in glassy Al shows a large valence instability, yielding an effective moment of 1.37..mu../sub B/ at room temperature to approx.0.25..mu../sub B/ at 5 K, which was not observed previously in an amorphous metal.