Electronic transport and thermal properties of CaB6 and Eu1−xCaxB6

By substituting Ca for Eu in EuB6, a local-moment ferromagnet, the transition temperature of 16 K for the binary compound, is lowered substantially with increasing x. In spite of the divalency of both Eu and Ca, significant changes in the electronic properties are indicated by changes in the temperature and magnetic-field dependences of the electrical resistivity, particularly at low temperatures. For pure CaB6 similar anomalies in the resistivity and the specific heat at very low temperatures as previously observed for SrB6, have been identified. Most of these properties most likely originate in the particular electronic structure of these hexaborides. (C) 2000 Elsevier Science B.V. All rights reserved.