Negative temperature coefficients of electrical resistivity: the divalent liquid metals Eu, Yb and Ba

Abstract

The electrical resistivities, rho , of Eu, Yb and Ba have been measured at high temperatures. In solid Yb and Ba rho varies linearly with temperature. This is contrary to some previous results. Both metals show a large percentage increase of rho on melting. The temperature dependence of rho in Eu is nonlinear and there is a smaller percentage change on melting. The resistivities of liquid Eu and Ba are larger than those of any other liquid metals. Negative temperature coefficients of resistivity are observed for all three metals in the liquid state. These results and those obtained in our earlier measurements on alloys of rare earth metals are discussed in the context of existing theories. The authors suggest that even in the liquid rare earth metals and their alloys an interpretation involving the liquid structure factors and the effective valences of the components may still provide a reasonable qualitative explanation of the behaviour of the resistivity. The occurrence of negative temperature coefficients in other disordered metallic systems is also commented on.