Thermodynamic properties of ferromagnetic mixed-spin chain systems

Noboru Fukushima, Andreas Honecker, Stefan Wessel, and Wolfram Brenig
Phys. Rev. B 69, 174430 – Published 28 May 2004
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Abstract

Using a combination of high-temperature series expansion, exact diagonalization, and quantum Monte Carlo, we perform a complementary analysis of the thermodynamic properties of quasi-one-dimensional mixed-spin systems with alternating magnetic moments. In addition to explicit series expansions for small spin quantum numbers, we present an expansion that allows a direct evaluation of the series coefficients as a function of spin quantum numbers. Due to the presence of excitations of both acoustic and optical nature, the specific heat of a mixed-spin chain displays a double-peak-like structure, which is more pronounced for ferromagnetic than for antiferromagnetic intrachain exchange. We link these results to an analytically solvable half-classical limit. Finally, we extend our series expansion to incorporate the single-ion anisotropies relevant for the molecular mixed-spin ferromagnetic chain material MnNi(NO2)4(ethylenediamine)2, with alternating spins of magnitude 5/2 and 1. Including a weak interchain coupling, we show that the observed susceptibility allows for an excellent fit and the extraction of microscopic exchange parameters.

  • Received 31 July 2003

DOI:https://doi.org/10.1103/PhysRevB.69.174430

©2004 American Physical Society

Authors & Affiliations

Noboru Fukushima1,*, Andreas Honecker1, Stefan Wessel2, and Wolfram Brenig1

  • 1Institut für Theoretische Physik, Technische Universität Braunschweig, D-38106 Braunschweig, Germany
  • 2Theoretische Physik, ETH Zürich, CH-8093 Zürich, Switzerland

  • *Electronic address: n.fukushima@tu-bs.de

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Vol. 69, Iss. 17 — 1 May 2004

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