16 - Comparison with experiment

Summary

Introduction

We have now seen in some detail how weak localisation and the interaction effect can modify the electron transport properties of electrons in metallic glasses or, more specifically, of electrons that are subject to strong elastic scattering, whether this be in the crystalline or the amorphous phase. What this survey shows is that many of the qualitative features to be expected are indeed observed in the resistivity, magnetoresistance and Hall coefficient of metallic glasses. The final question is: how far do the theories provide a quantitative account of the experiments?

It is at once clear, I think, why it is difficult to answer this question unequivocally. There are so many parameters that can influence the behaviour of these properties that unless some can be controlled or eliminated there are too many adjustable quantities to make possible a convincing comparison between theory and experiment.

One common way to overcome this problem is to make measurements of a range of properties so that a given specimen is very well characterised and as few as possible of the relevant parameters are left undetermined. So let us decide what quantities we know or can deduce with some reliability from experiment.

We can measure the low-temperature heat capacity of the metallic glass to find the term linear in temperature, which allows us to deduce the density of states at the Fermi level. In order to interpret the thermopower we would like to know the electron–phonon enhancement factor in the alloy; if it is a superconductor we can derive this from our knowledge of its superconducting properties.