Non-magnetic insulator state in Na1CoO2 and phase separation of Na vacancies

Abstract

Crystallographic, magnetic and NMR properties of a NaxCoO2 single crystal with x~1 are presented. We identify the stoichiometric Na1CoO2 phase, which is shown to be a non-magnetic insulator, as expected for homogeneous planes of Co3+ ions with S=0. In addition, we present evidence that, because of slight average Na deficiency, chemical and electronic phase separation leads to a segregation of Na vacancies into the well-defined, magnetic, Na0.8CoO2 phase. The importance of phase separation is discussed in the context of magnetic order for x~0.8 and the occurrence of a metal-insulator transition for x->1.

To appear in PRL

References in corpus (10)

• Coupling between electronic and structural degrees of freedom in the triangular lattice conductor NaxCoO2
• Magnetic ordering and spin waves in $\mathbf{N}{\mathbf{a}}_{0.82}\mathbf{Co}{\mathbf{O}}_2$
• Three-Dimensional Spin Fluctuations in Na0.75CoO2
• Series of Bulk Magnetic Phase Transitions in NaxCoO2: a muSR study
• 59Co NMR study of the Co states in superconducting and anhydrous cobaltates
• Charge ordering and magneto-polarons in Na${}_{0.82}$CoO${}_2$
• Metamagnetic Transition in Na${}_{0.85}$CoO${}_2$ Single Crystals
• Spin-Dynamics in the Carrier-Doped $S=1/2$ Triangular-Lattice of Na${}_x$CoO${}_2$-yH${}_2$O
• Investigation of the Spin Density Wave in NaxCoO2
• Synthesis, Characterization, and Magnetic Properties of gamma-NaxCoO2 (0.70 < x <0.84)

Cited by in corpus (23)

• Large enhancement of the thermopower in Na${}_x$CoO${}_2$ at high Na doping
• Patterning of sodium ions and the control of electrons in sodium cobaltate
• Magnetism and structure of LixCoO2 and comparison to NaxCoO2
• Low-lying quasiparticle states and hidden collective charge instabilities in parent cobaltate superconductors (NaxCoO2)
• Complete d-Band Dispersion and the Mobile Fermion Scale in NaxCoO2
• Na Induced Correlations in Na${}_x$CoO${}_2$
• Electronic texture of the thermoelectric oxide Na0.75CoO2
• Spin correlations and cobalt charge states: A new phase diagram of sodium cobaltates
• NQR and X-ray investigation of the structure of Na${}_{2/3}$CoO${}_2$ compound
• Direct link between low temperature magnetism and high temperature sodium order in NaxCoO2
• Melting of the Na layers in solid Na0.8CoO2
• Half-metallic Surface States and Topological Superconductivity in NaCoO${}_2$ from first principles
• Topotactic synthesis, structure and magnetic properties of a new hexagonal polytype of silver cobaltate(III) AgCoO2+δ
• 59Co NMR evidence for charge and orbital order in the kagome like structure of Na2/3CoO2
• Na order and Co charge disproportionation in Na${}_x$CoO${}_2$
• 23Na NMR study of sodium order in NaxCoO2 with 22K Neel temperature
• Spin polaron theory for the photoemission spectra of layered cobaltates
• Evolution of Co charge disproportionation with Na order in Na${}_x$CoO${}_2$
• Spin fluctuations, magnetic long-range order and Fermi surface gapping in NaxCoO2
• Comment on "Raman spectroscopy study of NaxCoO2 and superconducting NaxCoO2 yH2O"
• Hall effect evidence for an interplay between electronic correlations and Na order induced electronic bands topology in NaxCoO2
• A possibility of high spin hole states in doped CoO${}_2$ layered systems
• Sodium ion ordering of Na0.77CoO2 under competing multi-vacancy cluster, superlattice and domain formation