Münster 1997 – wissenschaftliches Programm

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AM: Magnetismus

AM 4: Elektronentheorie und Modelle geordneter Spinstrukturen II

AM 4.2: Vortrag

Montag, 17. März 1997, 15:30–15:45, F4

Magnetic order and chemical bonding in the High- T_C molecular-based cyanide magnets CsM[Cr(CN)₆], (M = Mn, Ni) from first principles — •V. Eyert¹, B. Siberchicot², and M. Verdaguer³ — ¹Hahn-Meitner-Institut, Glienicker Straße 100, D-14109 Berlin — ²CEA, Centre d’études de Limeil-Valenton, F-94195 Villeneuve-St-Georges — ³Laboratoire de Chimie des Métaux de Transition, 4 place Jussieu, F-75252 Paris

We present the results of first principles electronic structure calculations for the high Curie temperature magnetic insulators CsM[Cr(CN)₆] , M = Mn, Ni . Our density functional theory based calculations employ the augmented spherical waves (ASW) method. The chemical bonding is analyzed via the first ab initio calculation of the crystal orbital overlap population (COOP). The magnetic properties are explained by the orthogonality/overlap of magnetically active orbitals as studied by the COOP. Possible pathways for the exchange interaction are identified. In particular the sign of the exchange integrals between different effective magnetic sites is deduced. Excellent agreement with experimental data is found. While proving essential for the consistent understanding of electronic, magnetic and chemical properties of these materials our first principles approach moreover allows for the prediction and deeper understanding of the type of long-range magnetic order. Thereby it goes beyond the conclusions usually drawn from Goodenough-Kanamori superexchange rules or the model by Kahn and Briat.