Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 24: Postersitzung III: Korrelierte Elektronen, ”Orbital Physics”

TT 24.33: Poster

Mittwoch, 10. März 2004, 14:30–19:00, Poster A

Successful growth of the intermetallic compound CeCu₂(Si,Ge)₂ by high-temperature solution — •M. Deppe, H. S. Jeevan, R. Borth, C. Geibel, and F. Steglich — Max-Planck-Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dreden, Germany

Among the intermetallic compounds the system CeCu₂(Si,Ge)₂ is of high interest because of the interplay between heavy-fermion superconductivity and magnetism. For an intensive microscopic study large single crystals of high quality are necessary. Large single crystals of this compound were not available because of the incongruent formation of CeCu₂Si₂ and substantial loss of copper during the typical growing process. To overcome this difficulty the typical procedure is to use an off-stochiometric starting melt with an excess of copper. Four different ground states exist for CeCu₂Si₂ which are very sensitiv to the exact Cu/Si ratio. This makes it difficult to grow single crystals with a predetermind ground state. To overcome this problem we started the growth process with higher amount of Germanium because this reduced the variety of physical ground states to only one. Later on we reduce the Germanium content. We will discuss the optimal growth conditions for our modified Bridgman technique using copper as flux. For the physical characterisation we used resistivity and specific heat measurements. These measurements show that our crystal growth method gives reproducible results and evidence a systematic development of the magnetic state with increasing Germanium content in the concentration range x ≤ (0 - 0.5). The discussion will focus on the future optimization of our growth methods and the comparison with other crystal grow techniques.