Bayrakci S P, Mirebeau I, Bourges P, Sidis Y, Enderle M, Mesot J, Chen D P, Lin C T, Keimer B
Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
Phys Rev Lett. 2005 Apr 22;94(15):157205. doi: 10.1103/PhysRevLett.94.157205.
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.
Na x CoO₂是最近合成的超导体Na(x)CoO(2):yH₂O的母体化合物，对于0.75≤x≤0.9，在约20K以下呈现体反铁磁有序。我们进行了中子散射实验，在Na0.82CoO₂单晶中观察到了与A型反铁磁有序相对应的布拉格反射，并对相应的自旋波色散进行了表征。自旋波表现出强烈的能量依赖线宽。通过对最近邻海森堡模型拟合得到的面内和面外交换常数大小相似，鉴于Na x CoO₂的层状晶体结构，这是出乎意料的。讨论了这些观察结果可能的影响。
