Magnetic Phase Transition at 88 K in Na0.5CoO2 revealed by 23Na-NMR investigations

Abstract

Na0.5CoO2 exhibits a metal-insulator transition at 53 K upon cooling. The nature of another transition at 88 K has not been fully clarified yet. We report the results of measurements of the electrical conductivity, the magnetic susceptibility and 23Na NMR on a powder sample of Na0.5CoO2, including the mapping of NMR spectra, as well as probing the spin-lattice relaxation rate and the spin-spin relaxation rate, in the temperature range between 30 K and 305 K. The NMR data reflect the transition at T_X very well but provide less evidence for the metal-insulator transition at T_MI. The temperature evolution of the shape of the spectra implies the formation of a staggered internal field below T_X, not accompained by a rearrangement of the electric charge distribution. Our results thus indicate that in Na0.5CoO2, an unusual type of magnetic ordering in the metallic phase precedes the onset of charge ordering, which finally induces an insulating ground state.

11 pages, 9 figures; section 3 revised

References in corpus (6)

• 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
• Electron correlation and Fermi surface topology of Na${}_x$CoO${}_2$
• The Fermi surface of Na${}_x$CoO${}_2$
• Disproportionation Transition at Critical Interaction Strength: Na${}_{1/2}$CoO${}_2$
• Geometrical, electronic and magnetic properties of Na${}_{0.5}$CoO${}_2$ from first principles

Cited by in corpus (4)

• Searching for Stable Na-ordered Phases in Single Crystal Samples of gamma-NaxCoO2
• Melting of the Na layers in solid Na0.8CoO2
• ^{59}Co NMR evidence for charge ordering below T_{CO}\sim 51 K in Na_{0.5}CoO_2
• Temperature-driven transition from the Wigner Crystal to the Bond-Charge-Density Wave in the Quasi-One-Dimensional Quarter-Filled band