Magnetic properties of spin-orbital polarons in lightly doped cobaltates

Abstract

We present a numerical treatment of a spin-orbital polaron model for Na_xCoO_2 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.

4+ pages, 6 figures, accepted for publication in Phys. Rev. Lett

References in corpus (4)

• Fermi surface and quasiparticle dynamics of Na(x)CoO2 {x=0.7} investigated by Angle-Resolved Photoemission Spectroscopy
• ARPES on Na${}_{0.6}$CoO${}_2$: Fermi surface, extended flat dispersion, and unusual band splitting
• Three-Dimensional Spin Fluctuations in Na0.75CoO2
• Evidence of a single nonmagnetic Co3+ state in the Na1CoO2 cobaltate

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• Spin polaron theory for the photoemission spectra of layered cobaltates
• Electron-phonon interaction in the lamellar cobaltate Na${}_x$CoO${}_2$
• Novel electronic structure induced by a highly strained oxide interface with incommensurate crystal fields
• Dual electronic states in thermoelectric cobalt oxide
• Origin of the electron disproportionation in the metallic sodium cobaltates