Do we understand electron correlation effects in Gadolinium based intermetallic compounds?

Abstract

Recognising the difficulties in systematic understanding of the physical characteristics of strongly correlated f-electron systems, we considered it worthwhile to subject the so-called "normal" f-electron systems like those of Gd to careful investigations. We find that the spin-disorder contribution to electrical resistivity (p) in the paramagnetic state, instead of remaining constant, apparently shows an increase as the temperature (T) is lowered towards magnetic ordering temperature in some of the Gd alloys. In some cases, the T-dependence of "excess resistance" is so large that a distinct minimum in the plot of ρ versus T can be seen, mimicking the behaviour of Kondo lattices. This excess resistance can be suppressed by the application of a magnetic field, naturally resulting in large magnetoresistance. In addition, these alloys are found to exhibit heavy-fermion-like heat-capacity behavior. These unusual findings imply hither-to-unexplored electron correlation effects even in Gd-based alloys.