Electrical Resistivity Investigations on Metallic Rare-Earths

The study of transport properties is one of the classical disciplines in solid state physics. Nevertheless, there has been a rather late start in the progress towards a deeper understanding of transport in metallic rare earths (RE). At present there is, however, a quite satisfactory understanding of what one may characterize as normal resistivity behaviour.

In Section II we review theoretical models which have demonstrated their ability to account for the experimental results of normal resistivity behaviour in a variety of RE-systems, the crystal field only system TmSb, the low temperature ferromagnetic phase of Tb-metal and the intermediate systems TbcY1-cSb and HocY1-cSb.

In all cases these theoretical models treat the interactions between conduction electrons and localized 4f-electrons within the first Born-approximation. The electrical resistivities from such processes have in general a steady increase with temperature towards a saturation value, the spin-disorder resistivity, which results when all excitations in the 4f-system are equally populated.

Thus, normal resistivity behaviour is essentially a measure of thermal disorder but there are exceptions where negative temperature slopes may occur. The Kondo resonance scattering is, however, the most well known source of negative temperature slopes in the resistivity of metals with magnetic ions.