2003/10/28 by Jun Sugiyama, J. Sugiyama, J. H. Brewer +8
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Advanced Thermoelectric Materials and Devices #Physics of Superconductivity and Magnetism #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.69.214423
published as Physical Review B 69, 214423 (2004) · 8 pages, 6 figures
arxiv created 2003/10/28 · openalex publication_date 2004/06/24 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Magnetism of layered cobaltites NaxCoO2 with x=0.6 and 0.9 has been investigated by a positive muon spin rotation and relaxation (\ensuremathμ+SR) spectroscopy together with magnetic susceptibility and specific-heat measurements, using single-crystal samples in the temperature range between 250 and 1.8\phantom\rule0.3em0exK. Zero-field-(ZF-) \ensuremathμ+SR measurements on Na0.9CoO2 indicate a transition from a paramagnetic to an incommensurate spin-density wave state (IC-SDW) at 19\phantom\rule0.3em0exK(=TSDW). The anisotropic ZF-\ensuremathμ+SR spectra suggest that the oscillating moments of the IC-SDW direct along the c axis. Since Na0.6CoO2 is paramagnetic down to 1.8\phantom\rule0.3em0exK, the magnitude of TSDW is found to strongly depend on x. This behavior is well explained using the Hubbard model within a mean-field approximation on two-dimensional triangular lattice in the CoO2 plane. Also, both the appearance of the IC-SDW state by the change in x and the magnitude of the electronic specific-heat parameter of Na0.6CoO2 indicate that NaxCoO2 is unlikely to be a typical strongly correlated electron system.