NMR study of the magnetic and metal-insulator transitions in Na0.5CoO2: a nesting scenario

Abstract

Co and Na NMR are used to probe the local susceptibility and charge state of the two Co sites of the Na-ordered orthorhombic Na0.5CoO2. Above T_N=86K, both sites display a similar T-dependence of the spin shift, suggesting that there is no charge segregation into Co3+ and Co4+ sites. Below T_N, the magnetic long range commensurate order found is only slightly affected by the metal-insulator transition (MIT) at T_MIT=51K. Furthermore, the electric field gradient at the Co site does not change at these transitions, indicating the absence of charge ordering. All these observations can be explained by successive SDW induced by two nestings of the Fermi Surface specific to the x=0.5 Na-ordering.

4 pages, 4 figures

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• Charge and spin order on the triangular lattice -- Na${}_x$CoO${}_2$ at $x=0.5$
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• 59Co NMR evidence for charge and orbital order in the kagome like structure of Na2/3CoO2
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• Na order and Co charge disproportionation in Na${}_x$CoO${}_2$
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• Itinerant and localized magnetism on the triangular lattice: sodium rich phases of Na${}_x$CoO${}_2$
• Rearrangement of Sodium ordering and its effect on physical properties in $N{a}_{x}Co{O}_2$ system
• Interplay between Magnetism and Na concentration in $N{a}_{x}Co{O}_2$
• Evolution of Co charge disproportionation with Na order in Na${}_x$CoO${}_2$
• Na-ion dynamics in Quasi-1D compound NaV2O4
• Localized versus itinerant magnetic moments in Na0.72CoO2
• Emergent charge ordering in near half doped Na${}_{0.46}$CoO${}_2$
• Synthesis of sodium cobaltate Na${}_x$CoO${}_2$ single crystals with controlled Na ordering
• Ionic Hubbard model on a triangular lattice for Na_0.5CoO_2, Rb_0.5CoO_2 and K_0.5CoO_2: Mean-field slave boson theory
• Pressure effects in the triangular layered cobaltites NaxCoO2
• Theory of carrier concentration-dependent electronic behavior in layered cobaltates
• New electronic orderings observed in cobaltates under the influence of misfit periodicities
• NMR studies of Successive Phase Transitions in Na0.5CoO2 and K0.5CoO2
• Electronic and magnetic properties of the ionic Hubbard model on the striped triangular lattice at 3/4 filling
• Phonon softening and "forbidden" mode observed by Raman scattering in Na0.5CoO2
• Complex magnetic differentiation of cobalts in Na${}_x$CoO${}_2$ with 22K Néel temperature
• Magnetic field induced spin-flop transition in Na${}_x$CoO${}_2$ (0.5$<$x$<$0.55)
• Hall effect evidence for an interplay between electronic correlations and Na order induced electronic bands topology in NaxCoO2
• Magnetotransport properties in purple bronze Li${}_{0.9}$Mo${}_6$O${}_{17}$ Single Crystal
• Temperature-driven sodium-ion dynamical-to-static crossover in the zig-zag ordered phase of Na${}_{0.5}$CoO${}_2$
• Quasiparticle dispersion near the Fermi surface in Na${}_x$CoO${}_2$