On the Origin of the Metallic and Anisotropic Magnetic Properties of Na_xCoO_2 (x~~0.75)

M. -H. Whangbo; D. Dai; R. K. Kremer

Home/Archive/arXiv

arXiv · cond-mat/0606103

On the Origin of the Metallic and Anisotropic Magnetic Properties of Na_xCoO_2 (x~~0.75)

M. -H. Whangbo·D. Dai·R. K. Kremer

View original source ↗Read source document ↗Export metadata ↓

Abstract

Non-stoichiometric NaxCoO2 (0.5 < x < 1) consists of CoO2 layers made up of edge-sharing CoO6 octahedra, and exhibits strongly anisotropic magnetic susceptibilities as well as metallic properties. A modified Curie-Weiss law was proposed for systems containing anisotropic magnetic ions to analyze the magnetic susceptibilities of NaxCoO2 (x ~~ 0.75), and implications of this analysis were explored. Our study shows that the lowspin Co4+ (S = 1/2) ions of NaxCoO2 generated by the Na vacancies cause the anisotropic magnetic properties of NaxCoO2, and suggests that the six nearest-neighbor Co3+ ions of each Co4+ ion adopt the intermediate-spin electron configuration thereby behaving magnetically like low-spin Co4+ ions. The Weiss temperature of NaxCoO2 is more negative along the direction of the lower g-factor (i.e., Theta_parallel < Theta_perp < 0, and g_parallel < g_perp). The occurrence of intermediate-spin Co3+ ions surrounding each Co4+ ion account for the apparently puzzling magnetic properties of NaxCoO2 (x ~~ 0.75), i.e., the large negative Weiss temperature, the three-dimensional antiferromagnetic ordering below ~22 K, and the metallic properties. The picture of the magnetic structure derived from neutron scattering studies below ~22 K are in apparent conflict with that deduced from magnetic susceptibility measurements between ~50 - 300 K. These conflicting pictures are resolved by noting that the spin exchange between Co3+ ions is more strongly antiferromagnetic than that between Co4+ and Co3+ ions.

Explore related subjects

cond-mat.str-el cond-mat.mtrl-sci

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

M. -H. Whangbo, D. Dai, R. K. Kremer. 2006-06-05. On the Origin of the Metallic and Anisotropic Magnetic Properties of Na_xCoO_2 (x~~0.75). https://arxiv.org/abs/cond-mat/0606103

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Real-space determination of orbital states driving successive phase transitions in FeV2O4

Direct experimental access to orbital states in strongly correlated materials remains a major challenge, despite their central role in driving coupled structural and magnetic phase transitions. In systems where electronic correlations, electron-lattice coupling, and relativistic spin-orbit interactions compete on comparable energy scales, even first-principles calculations often yield multiple metastable solutions, hindering the unambiguous identification of the ground state. Here, we demonstrate that the orbital states of the spinel oxide FeV2O4, which possesses active orbital degrees of freedom on both Fe and V ions, are uniquely resolved by combining valence electron density (VED) analysis based on state-of-the-art synchrotron x-ray diffraction with spin-polarized density-functional-theory calculations. Our results reveal that temperature-dependent rearrangements of orbital occupations drive successive structural transitions that accompany collinear and noncoplanar ferrimagnetic orders, establishing a direct correspondence between orbital anisotropy and spin structure. More broadly, this work shows that experimentally determined VED provides a decisive real-space constraint on competing theoretical solutions, offering a powerful and broadly applicable framework for elucidating the microscopic mechanisms of complex phase transitions in strongly correlated electron systems.

cond-mat.str-el↗

arXiv2026

Macroscopic Zero-Mode Manifold Isolated by Quantum Chaos

Chaotic many-body spectra are expected to densely fill their energy window. We show that constrained spin chains with chiral symmetry evade this expectation by hosting an exponentially large manifold of symmetry-protected exact zero modes separated from the surrounding spectrum by a sharp gap at zero energy. The gap is generated by chaotic level repulsion, with width set by the number of zero modes times the mean level spacing. We verify this mechanism in an East-West kinetically constrained chain, develop a minimal random-matrix description, and show how the gap can be detected through linear-response spectroscopy.

cond-mat.str-el↗

arXiv2026

Textures as a phase-transition probe for quantum spin chains

The idea of quantum texture has been recently proposed and used as a tool for quantifying coherences and for quantum gate identification. In this work we offer a study on its usage to quantum phase transitions, demonstrating the rugosity metric as a simple tool for effective phase-transition probing. We establish the link between rugosity in the computational basis and the hierarchy of spin correlators, and analyze rugosities defined in the global ground-state and in ground-states belonging to different magnetization sectors (to which we refer to as global vs symmetry-resolved rugosities) to study the phase diagram of the Heisenberg XXZ model. We find distinct rugosity signatures at both transition points. In particular, a sharp feature appears at $Δ=1$ already for small systems, revealing a pronounced sensitivity of the correlation hierarchy encoded by the texture to this point. Since the BKT transition coincides with the isotropic $SU(2)$ point of the XXZ model, this behavior may reflect a particular sensitivity of rugosity to the structure of the spin-correlation hierarchy at isotropy.

cond-mat.str-el↗