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 5 and EuAu 5 with the hexagonal structure by the Bridgman method. Both compounds are known to be ferromagnets with Curie temperatures T C = 57 and 13 K, respectively, and the Eu-4f magnetic moments of EuCu 5 are known to orient along the hexagonal c-axis or the [0001] direction by the Mössbauer experiment. The magnetisations at 2 K in EuCu 5 and EuAu 5 in the present experiment saturate at an extremely low field of 2 kOe for H ∥ [ 0001 ] , with a Eu 2 + -moment of 7 μ B / E u . On the other hand, the hard-axis magnetisations for H ⊥ [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 J ∥ [0001] in EuCu 5 and EuAu 5 are about 10 μ Ω ⋅ c m at room temperature, which are compared with the resistivities of ρ = 30–40 μ Ω ⋅ c m for J ⊥ [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 5 , revealing the existence of a large plate-like Fermi surface. [ABSTRACT FROM AUTHOR]