Electronic transport in Eu1-xCaxB6

We have measured the electrical resistivity, the magnetoresistance, the Hall effect, and the magnetization in varying temperature ranges between 0.3 and 300 K on single crystals of EuB6, CaB6, and Eu0.8Ca0.2B6. The ferromagnetic phase transition of EuB6, marked by a sharp peak in the temperature dependence of the electrical resistivity p(T) just below 16 K, is shown to be accompanied by a considerable increase of the effective charge carrier concentration n(eff). The overall features of the transport properties of Eu0.8Ca0.2B6 are similar to those of EuB6. A phase transition at 5.3 K has been established. However, the increase of n(eff) across this phase transition by two orders of magnitude is much more pronounced than in pure EuB6.