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Lecture D.I. Khomskii


24 mei 2006 FWN-Building 5113.0201, Nijenborgh 4, 9747 AG, Groningen
Speaker:Prof. Dr. D.I. Khomskii
Affiliation:II Physikalisches Institut, Universitaet zu Koeln, Germany
Title:Superstructures and spin gaps caused by orbital ordering
Date:Wed May 24, 2006
Location:FWN-Building 5113.0201
Host:M. Mostovoy
Telephone:+31 50 363 3419


I will discuss the origin of complex superstructures in B-spinels showing interplay of charge, spin and orbital degrees of freedom. In particular, for MgTi2O4, and CuIr2S4 we proposed the picture of orbitally-driven Peierls state with the spin gaps on metal dimers. A similar mechanism can explain spin gap in the pyroxene NaTiSi2O6 and La4Ru2O10. In Tl2Ru2O7 orbital ordering may lead to the formation of Haldane chains. Finally, I propose a model of charge and orbital ordering in magnetite based on interplay between site- and bond-centered ordering, which seems to explain both the structural data and the presence of ferroelectricity in Fe3O4 below Verwey transition.
Laatst gewijzigd:22 oktober 2012 14:30