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AM: Magnetismus

AM 2: Magnetische Phasenüberg
änge, Elektronentheorie

AM 2.6: Talk

Monday, March 26, 2001, 11:30–11:45, S 5.4

Structural and physical properties of Eu₈Ga₁₆Ge₃₀ — •A. Bentien, S. Paschen, W. Carrillo-Cabrera, M. Baenitz, V.H. Tran, Yu. Grin, and F. Steglich — MPI für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, D - 01187 Dresden

Clathrates are solids made up of large cages of silicon, germanium, or tin (or, in the well-known gashydrate-clathrate-I, of H₂O) which encapsulate guest atoms. Eu₈Ga₁₆Ge₃₀ is the only clathrate known so far where the guest positions are fully occupied by a rare-earth element. Our investigations show that, in addition to the previously synthesized Eu₈Ga₁₆Ge₃₀ phase with clathrate-I structure, there exists a second Eu₈Ga₁₆Ge₃₀ phase with clathrate-III structure. Both phases behave as local-moment ferromagnets with relatively low Curie temperatures (9.5 and 35 K). The temperature dependences of the electrical resistivities are metallic in nature but the charge-carrier concentrations are quite small. The low Curie temperatures and the small charge-carrier concentrations may indicate that we are not too far from our initial goal, namely from obtaining a non-magnetic semiconductor.