The electronic transport properties of amorphous metallic alloys
Amorphous metals have been studied extensively recently and possess many interesting electronic properties. This thesis aims to examine some of these, with particular reference to the conductivity and Hall effect in such alloys. In an extensive review of recent theoretical and experimental work, the author attempts to examine (i) whether the data can be explained using the 'semi-classical' theory of transport, with the inbuilt assumption that the electron loses memory of all collisions before that immediately preceding the time of observation, or whether 'quantum interference' and 'electron correlation phenomena must be considered, and (ii) whether it is possible to provide a simple physical picture of such quantum interference phenomena which leads to results commensurate with those of formal theories and with experimental results. A good probe of electron correlation effects is the temperature dependence of the Hall coefficient. In conjunction with the conductivity a good idea of the importance of such phenomena can be obtained. The succeeding chapters discuss the rebuilding of a radio frequency sputtering system suitable for production of thin amorphous metal films, and the methods used in making high precision measurements of the properties mentioned, between 1.25 and 300K. A results chapter reports data taken on the Cu-Ti and Ni-Zr systems, which were chosen as representative transition metal - transition metal alloy systems showing a wide range of behaviour. Extensive analysis of these data is undertaken, in terms of quantum interference and other theories. The effects of clustering of magnetic centres, and of superconductivity, in Ni-Zr films, is discussed. It is shown that the results are in broad agreement with these theories and first evidence is presented that electron correlation phenomena may be affected by inelastic electron scattering at intermediate temperatures. Confirmation of a simple relationship between the change in Hall coefficient and of conductivity due to electron correlation, predicted by theory, is provided. A short conclusion makes suggestions for future experimental work.