2005/08/31 by B. Pedrini, Bill Pedrini, J. L. Gavilano +10
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Magnetic and transport properties of perovskites and related materials #Physics of Superconductivity and Magnetism #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.72.214407
published as Physical Review B 72, 214407 (2005) · 11 pages, 9 figures; section 3 revised
openalex publication_date 2005/12/06 · arxiv created 2006/02/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Na0.5CoO2 exhibits a metal-insulator transition at TMI=53\phantom\rule0.3em0exK upon cooling. The nature of another transition at TX=88\phantom\rule0.3em0exK has not been fully clarified yet. We report the results of measurements of the electrical conductivity \ensuremathσ, the magnetic susceptibility \ensuremathχ 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 T\phantom\rule0.2em0ex1^\ensuremath-1(T) and the spin-spin relaxation rate T\phantom\rule0.2em0ex2^\ensuremath-1(T), in the temperature range between 30 and 305\phantom\rule0.3em0exK. The NMR data reflect the transition at TX very well but provide less evidence for the metal-insulator transition at TMI. The temperature evolution of the shape of the spectra implies the formation of a staggered internal field below TX, 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.