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| VOLUME 84 | ISSUE 12 |
PAGE 769
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| Electronic theory for itinerant in-plane magnetic fluctuations in NaxCoO2 |
M. M. Korshunov*+, I. Eremin , A. Shorikov , V. I. Anisimov
*L.V. Kirensky Institute of Physics, Siberian Branch of RAS, 660036 Krasnoyarsk, Russia
+ Max-Planck-Institut für Physik komplexer Systeme, D-01187 Dresden, Germany
 Institut für Mathematische Physik and Theoretische Physik, TU Braunschweig, 38106 Braunschweig, Germany
Institute of Metal Physics, RAS-Ural Division, 620041 Yekaterinburg GSP-170, Russia
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PACS: 31.15.Ar, 71.10.-w, 74.70.-b, 75.40.Cx
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Abstract
Starting from ab-initio band structure for NaxCoO2, we
derive the single-electron energies and the effective tight-binding
description for the t2g 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 Γ
point of the first Brillouin zone forms. Therefore, in addition to a
large Fermi surface an electron pocket close to the Γ 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
xm, in agreement with neutron scattering data. Below xm the
magnetic susceptibility shows a tendency towards the
antiferromagnetic fluctuations. We estimate the value of
0.56 < xm < 0.68 within the rigid band model and within the Hubbard
model with infinite on-site Coulomb repulsion consistent with the
experimental phase diagram.
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