Magnetic ordering and spin waves in $\bf Na_{0.82}CoO_2$

S. P. Bayrakci; I. Mirebeau; P. Bourges; Y. Sidis; M. Enderle; J. Mesot; D. P. Chen; C. T. Lin; B. Keimer

doi:10.1103/PhysRevLett.94.157205

paper

Magnetic ordering and spin waves in $N a_{0.82} Co O_{2}$

arXiv:cond-mat/0410224 · doi:10.1103/PhysRevLett.94.157205

Abstract

Na $_{x}$ CoO $_{2}$ , the parent compound of the recently synthesized superconductor Na $_{x}$ CoO $_{2}$ : $y$ H $_{2}$ O, exhibits bulk antiferromagnetic order below $\sim 20$ K for 0.75 $\leq x \leq$ 0.9. We have performed neutron scattering experiments in which we observed Bragg reflections corresponding to A-type antiferromagnetic order in a Na $_{0.82}$ CoO $_{2}$ 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 Na $_{x}$ CoO $_{2}$ . Possible implications of these observations are discussed.

final version, to appear in PRL

Magnetic ordering and spin waves in Na0.82​CoO2​

Abstract

Magnetic ordering and spin waves in $N a_{0.82} Co O_{2}$