Electrical Resistivity near the Magnetic Transition of Some Rare-Earth Laves Phase Compounds

From the measured temperature dependence of the electrical resistivity ρ(T), we have computed the temperature derivative dρdT with particular emphasis on its behavior in the critical region for six ferromagnetic rare-earth cubic Laves phase compounds: GdAl₂, GdCo₂, GdNi₂, GdPt₂, GdRh₂, and DyAl₂. All samples are characterized by pronounced changes in dρdT in the vicinity of the magnetic ordering temperature Tc. In GdNi₂, GdPt₂, and GdRh₂, as the temperature is decreased toward Tc, a minimum in dρdT, followed by a maximum, is observed. This behavior is consistent with that predicted from the long-range nature of the short-range spin fluctuations in the framework of the molecular field theory. The behavior of dρdT for GdAl₂ and DyAl₂ shows only a broad maximum, whereas for GdCo₂, dρdT has a sharp peak at about Tc --- very similar to that found in transition metals.