Regensburg 2019 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 17: Poster Session: Correlated Electrons 1
TT 17.22: Poster
Monday, April 1, 2019, 15:00–18:30, Poster D
Interchain mean-field theory for thermodynamic properties of a bimetallic ferromagnetic spin-chain compound — •Maheshwor Tiwari1, Stefan Süllow2, Matthias Bleckmann2, Ralf Feyerherm3, Wolfram Brenig4, and Andreas Honecker1 — 1Laboratoire de Physique Théorique et Modélisation, CNRS UMR 8089, Université de Cergy-Pontoise, France — 2Institut für Physik der Kondensierten Materie, Technische Universität Braunschweig, Germany — 3Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany — 4Institut für Theoretische Physik, Technische Universität Braunschweig, Germany
Two energy scales are observed in the field-dependent specific heat of MnNi(NO2)4(en)2, en = ethylenediamine, containing ferromagnetically coupled chains with alternating spins of magnitude 1 and 5/2. MnNi(NO2)4(en)2 orders antiferromagnetically at low temperatures in low magnetic fields, demonstrating relevant antiferromagnetic interchain coupling, with a suppression of this order already by a weak magnetic field.
Here we present numerical results for the specific heat obtained by exact diagonalization and Quantum-Monte-Carlo simulations for the alternating spin chain model, using parameters that have been derived from the high-temperature behavior of the magnetic susceptibility. The interchain coupling is included in the numerical treatment at the mean-field level. The observed strong effect of an applied magnetic field on the ordered state promises interesting magnetocaloric properties that we explore theoretically.