Quasi-one-dimensional Magnetic Interactions and Conduction Electrons in EuCu5 and EuAu5 with the Characteristic Hexagonal Structure

We have succeed in growing single crystals of EuCu and EuAu with the hexagonal structure by the Bridgman method. Both compounds are known to be ferromagnets with Curie temperatures and 13 K, respectively, and the Eu-4f magnetic moments of EuCu are known to orient along the hexagonal c-axis or the [0001] direction by the Mossbauer experiment. The magnetisations at 2 K in EuCu and EuAu in the present experiment saturate at an extremely low field of 2 kOe for , with a Eu-moment of . On the other hand, the hard-axis magnetisations for [0001] saturate at a high field of 40 kOe. It is also found from the electrical resistivty measurement that the electrical resistivities along the current [0001] in EuCu and EuAu are about at room temperature, which are compared with the resistivities of 30-40 for [0001]. The quasi-one dimensional conductivities are also characteristic, which were clarified from the de Haas-van Alphen (dHvA) experiment and FLAPW energy band calculation for EuAu, revealing the existence of a large plate-like Fermi surface.