Electronic transport in EuB6 -: art. no. 125118

EuB6 is a magnetic semiconductor in which defects introduce charge carriers into the conduction band with the Fermi energy varying with temperature and magnetic field and which orders ferromagnetically via two consecutive phase transitions at 15.5 and 12.5 K, respectively. We present a consistent analysis of the temperature- and magnetic-field dependences of the electrical resistivity and of the Hall effect of a single-crystalline sample at temperatures between 22.5 and 300 K, as well as between 2 and 8 K, avoiding the critical transition region. The covered magnetic-field range was between 0 and 5.5 T. The negative magnetoresistance is well reproduced by a model in which the spin disorder scattering is reduced by the applied magnetic field. The Hall effect can be separated into an ordinary and an anomalous part. At 22.5 K the latter accounts for half of the observed Hall voltage, and its importance decreases rapidly with increasing temperature. As for Gd and its compounds, where the rare-earth ion adopts the same Hund's rule ground state as Eu2+ in EuB6, the standard antisymmetric scattering mechanisms underestimate the size of this contribution by several orders of magnitude, while reproducing its shape almost perfectly. Well below the bulk ferromagnetic ordering at T-C = 12.5 K, a two-band model successfully describes the magnetotransport. Our description is consistent with published de Haas-van Alphen, optical reflectivity, angular-resolved photoemission, and soft x-ray emission as well as absorption data, but requires a new interpretation for the gap feature deduced from the latter two experiments.