Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 13: Symposium “Superconductivity and Magnetism in Lamellar Cobaltates”

TT 13.5: Talk

Tuesday, March 27, 2007, 16:05–16:30, H18

Magnetic properties of spin-orbital polarons in lightly doped cobaltates — •Maria Daghofer, Peter Horsch, and Giniyat Khaliullin — MPI for Solid State Research, Stuttgart, Germany

We present a numerical treatment of a spin-orbital polaron model for Na_xCoO₂ at small hole concentration (0.7 < x< 1). We demonstrate how the polarons account for the peculiar magnetic properties of this layered compound: They explain the large susceptibility; their internal degrees of freedom lead both to a negative Curie-Weiss temperature and yet to a ferromagnetic intra-layer interaction, thereby resolving a puzzling contradiction between these observations. We make specific predictions on the momentum and energy location of excitations resulting from the internal degrees of freedom of the polaron, and discuss their impact on spin-wave damping.