On the Anomalous Physical Properties of Liquid Copper Alloys

Magnetic susceptibilities and electrical resistivities of the liquid copper alloys, Cu-Bi, Cu-Sn and Cu-In have been measured as functions of chemical compositions at temperatures in the neighbourhood of 1000℃. In the liquid Cu-Bi alloy, observed magnetic susceptibility and electrical resistivity are well explained in terms of a model which assumes random distribution of Cu and Bi ions in an free electron gas atmosphere. In the liquid Cu-Sn and Cu-In alloys, anomalous behaviours are observed in their magnetic susceptibility and electrical resistivity. It is shown that the observed deep valleys of diamagnetism in the magnetic susceptibility curves of both liquid alloys correspond to the peaks in the curves of the heat of mixing for the respective alloys observed in our previous report. The observed values of magnetic susceptibility are compared with theoretical curves calculated by taking account of a contribution from n_R pseudo-molecules which are formed by association of Cu ions with Sn or In ion. It is found that about two electrons are localized in a pseudo-molecule for both liquid alloys near 1100℃ and that the observed deep diamagnetism originates from the existence of pseudo-molecules. Electrical resistivities for both kinds of liquid alloys are given as the sum of contributions from scattering of conduction electrons by randomly distributed free ions and by pseudo-molecules. The contribution ρ_1 caused by the former mechanism can be estimated in terms of a hard sphere model for the Ashcroft potential, and the latter contribution ρ_2 can be assumed to be in proportion with the distribution function n_R of the pseudo-molecule in the liquid alloy on the bases of its flexible structure. For both kinds of alloys such a proportional relationship is regarded as a reasonable assumption because the n_R curve behaves similarly to that of ρ_2=ρ-ρ_1 versus alloying compositions, where ρ is the observed total resistivity