Electronic theory for itinerant in-plane magnetic fluctuations in NaCoO
arXiv:cond-mat/0608327 · doi:10.1134/S0021364006240040
Abstract
Starting from {\it ab-initio} band structure for NaCoO, we derive the single-electron energies and the effective tight-binding description for the bands using a projection procedure. We find that due to the presence of the next-nearest-neighbor hoppings a local minimum in the electronic dispersion close to the point of the first Brillouin zone forms. Therefore, in addition to a large Fermi surface an electron pocket close to the point emerges at high doping concentrations. The latter yields the new scattering channel resulting in a peak structure of the itinerant magnetic susceptibility at small momenta. This indicates itinerant in-plane ferromagnetic state above certain critical concentration , in agreement with neutron scattering data. Below the magnetic susceptibility shows a tendency towards the antiferromagnetic fluctuations. We estimate the value of within the rigid band model and within the Hubbard model with infinite on-site Coulomb repulsion consistent with the experimental phase diagram.
4 pages, 4 figures; LDA calculations were done with Na in the symmetric 2d position contrary to the 6h position in a previous version of this paper
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