Dresden 2006 – wissenschaftliches Programm

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DF: Dielektrische Festkörper

DF 10: Electric, Electromechanical and Optical Properties I

DF 10.1: Hauptvortrag

Donnerstag, 30. März 2006, 14:30–15:10, M{\"U}L Elch

Broadband Dielectric Spectroscopy in Functional Transition-Metal Compounds — •Joachim Hemberger, Peter Lunkenheimer, Robert Fichtl, Stefan Weber, Torsten Rudolf, Franz Mayer, Andrei Pimenov, Vladimir Tsurkan, and Alois Loidl — Center for Electronic Correlation and Magnetism, University of Augsburg, D-85135 Augsburg, Germany

Transition-metal compounds offer an exceptional variety of functional properties with a broad range of application. In addition to the canonical dielectric oxides reaching from piezo-electric or ferroelectric to high-permittivity materials, compounds with complementary magnetic and electronic properties are currently more and more under focus. An example are multiferroic compounds combining ferroelectricity and ferromagnetism. However, the coexistence of magnetic spin, orbital or charge degrees of freedom requires the consideration of systems with partially filled d-shells in contrast to the usual dielectric d⁰-systems. This is accompanied by an deterioration of the insulating properties. Non-d⁰ systems commonly are "bad insulators", i.e. they posses smaller, correlation induced electronic gaps instead of the large band gaps of usual optically transparent dielectric materials. This leads to finite DC- and AC-contributions to the conductivity and to a finite charge carrier density in the conduction band. The talk will outline the potential as well as the difficulties of broadband dielectric spectroscopy to study complex transition-metal compounds and illustrate them discussing various examples like titanates, manganates or Cr-based thio-spinels.

This work was supported by BMBF (VDI/EKM 13N6917-A) and DFG (SFB 484).