Electronic transport and thermal properties of CaB6 and Eu1-xCaxB6

By substituting Ca for Eu in EuB6, a local-moment ferromagnet, the transiti on temperature of 16 K for the binary compound, is lowered substantially wi th increasing x. In spite of the divalency of both Eu and Ca, significant c hanges in the electronic properties are indicated by changes in the tempera ture and magnetic-field dependences of the electrical resistivity, particul arly at low temperatures. For pure CaB6 similar anomalies in the resistivit y 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 Else vier Science B.V. All rights reserved.