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TT: Tiefe Temperaturen

TT 11: Postersitzung II (Metall-Isolator-Überg
änge, Phasenüberg
änge in Quantensystemen, Theorie: Systeme korrelierter Elektronen)

TT 11.37: Poster

Dienstag, 25. März 2003, 14:30–19:00, P2c, P2d

High-temperature series expansion for mixed-spin chains — •Noboru Fukushima, Andreas Honecker, and Wolfram Brenig — Institut für Theoretische Physik, Technische Universität Braunschweig, Germany

We perform high-temperature series expansions for the specific heat and the susceptibility of the Heisenberg chain with alternating spins. The coefficients of the series are obtained as analytic functions for arbitrary spin. A comparison will be presented between our series and results from exact diagonalizations of finite systems. Particular emphasis will be on a discussion of the differences between ferromagnetic and antiferromagnetic exchange interactions. In addition the impact of exchange alternation and/or single ion anisotropy will be investigated. The latter could be of importance for the interpretation of thermodynamic data obtained on the molecular magnet MnNi(NO₂)₄(ethylendiamine)₂.