2003/12/11 by P. Carretta, M. Mariani, Manuel Mariani +11 · 3 citations
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.str-el
paper · pdf · doi:10.1103/physrevb.70.024409
14 figures
arxiv created 2003/12/11 · openalex publication_date 2004/07/13 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Nuclear magnetic resonace (NMR), EPR and magnetization measurements in NaxCoO2 for 0.65\ensuremath\leqslantx\ensuremath\leqslant0.75 are presented. While the EPR signal arises from Co4+ magnetic moments ordering at Tc\ensuremath≃26\phantom\rule0.3em0exK, 59Co NMR signal originates from cobalt nuclei in metallic regions with no long range magnetic order and characterized by a generalized susceptibility typical of strongly correlated metallic systems. This phase separation in metallic and magnetic insulating regions is argued to occur below T*(x) (220--270\phantom\rule0.3em0exK). Above T* an anomalous decrease in the intensity of the EPR signal is observed and associated with the delocalization of the electrons which for T<T* were localized on Co4+\phantom\rule0.3em0exd_z2 orbitals. It is pointed out that the in-plane antiferromagnetic coupling J⪡T* cannot be the driving force for the phase separation.