title: Magnetic ordering and spin waves in Na0.82CoO2.
abstract: NaxCoO2, the parent compound of the recently synthesized superconductor Na(x)CoO(2):yH(2)O, exhibits bulk antiferromagnetic order below approximately 20 K for 0.75</=x</=0.9. We have performed neutron scattering experiments in which we observed Bragg reflections corresponding to A-type antiferromagnetic order in a Na0.82CoO2 single crystal and characterized the corresponding spin-wave dispersions. The spin waves exhibit a strongly energy-dependent linewidth. The in-plane and out-of-plane exchange constants resulting from a fit to a nearest-neighbor Heisenberg model are similar in magnitude, which is unexpected in view of the layered crystal structure of NaxCoO2. Possible implications of these observations are discussed.
authors.affiliation: Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
authors.forename: S P
authors.initials: SP
authors.lastname: Bayrakci
authors.forename: I
authors.initials: I
authors.lastname: Mirebeau
authors.forename: P
authors.initials: P
authors.lastname: Bourges
authors.forename: Y
authors.initials: Y
authors.lastname: Sidis
authors.forename: M
authors.initials: M
authors.lastname: Enderle
authors.forename: J
authors.initials: J
authors.lastname: Mesot
authors.forename: D P
authors.initials: DP
authors.lastname: Chen
authors.forename: C T
authors.initials: CT
authors.lastname: Lin
authors.forename: B
authors.initials: B
authors.lastname: Keimer