Berlin 2008 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 18: Correlated Electrons: Low-dimensional Systems - Materials 2
TT 18.13: Vortrag
Dienstag, 26. Februar 2008, 18:30–18:45, H 2053
Microscopic simulation and analysis of a spin crossover transition — •Harald O. Jeschke1, L. Andrea Salguero1, Badiur Rahaman2, Christian Buchsbaum3, Volodymyr Pashchenko3, Martin U. Schmidt3, Tanusri Saha-Dasgupta2, and Roser Valenti1 — 1Institut für Theoretische Physik, Universität Frankfurt, Max-von-Laue-Str. 1, 60438 Frankfurt, Germany — 2S.N. Bose National Centre for Basic Sciences, JD Block, Sector 3, Salt Lake City, Kolkata 700098, India — 3Institut für Anorganische und Analytische Chemie, Universität Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt, Germany
In spin crossover materials, an abrupt phase transition between a low spin state and a high spin state can be driven by temperature, pressure or illumination. Of a special relevance are Fe(II) based coordination polymers where, in contrast to molecular systems, the phase transition shows a pronounced hysteresis which is desirable for technical applications. A satisfactory microscopic explanation of this large cooperative phenomenon has been sought for a long time. The lack of X-ray data has been one of the reasons for the absence of microscopic studies. In this work, we present an efficient route to prepare reliable model structures and within ab initio density functional theory analysis and effective model considerations we show that in polymeric spin crossover compounds magnetic exchange between high spin Fe(II) centres is as important as elastic couplings for explaining the considerable cooperativity and thus the width of the hysteresis.