Influence of Structural Relaxation Upon the Low Temperature Properties of Metallic Glasses

摘要

Below 1K, the thermal conductivity of metallic glasses (Fe sub 40 Ni sub 40 P sub 14 B sub 6 , Pd sub 77 sub 5 Si sub 16 sub 5 Cu sub 6 and Zr sub 3 Rh) is similar to that of the large class of amorphous materials. The influence of the electron-phonon interaction upon the phonon thermal conductivity kappa/sub ph/ (T < 1K) in PdSiCu agree well with theoretical prediction. We have found no effect upon kappa/sub ph/ due to boundary scattering in our samples. We have deduced the glassy thermal conductivity kappa/sub glass/ for Zr sub 3 Rh and PdSiCu from our measurements, where 1/kappa/sub glass/ is the thermal resistivity intrinsic to the disordered state of the solid. The thermal conductivity kappa/sub glass/ of glassy metals was shown to change reversibly with heat treatment at temperature T/sub A/ near the glass transition. Results were compared with a model of the glass transition and structural relaxation based upon a free-volume approach, developed by Cohen, Turnbull and Grest (CTG). The CTG model suggests that the two-level states (TLS) should be assigned to the tunneling of atoms adjacent to voids. The number of voids (or TLS, N(E)) is related by CTG directly to the free volume. A quantitative relation between free volume and the metastable equilibrium temperature of the glass is suggested by the CTG model. We associate the metastable equilibrium temperature with our anneal temperature T/sub A/; in this context the CTG model predicts N(E) proportional to T/sub A/. This prediction is consistent with observations of a reversible change of N(E) in metallic glasses upon anneal. (ERA citation 08:051636)