Schweika W, Valldor M, Lemmens P
Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich, Germany.
Phys Rev Lett. 2007 Feb 9;98(6):067201. doi: 10.1103/PhysRevLett.98.067201. Epub 2007 Feb 7.
Y0.5Ca0.5BaCo4O7 contains kagomé layers of Co ions, whose spins are strongly coupled, with a Curie-Weiss temperature of -2200 K. At low temperature, T=1.2 K, our diffuse neutron scattering study with polarization analysis reveals characteristic spin correlations close to a predicted two-dimensional coplanar ground state with staggered chirality. The absence of three-dimensional long-range antiferromagnetic order indicates negligible coupling between the kagomé layers. The scattering intensities are consistent with high spin S=3/2 states of Co2+ in the kagomé layers and low spin S=0 states for Co3+ ions on interlayer sites. Our observations agree with previous Monte Carlo simulations indicating a ground state of effectively short range, staggered chiral spin order.
Y0.5Ca0.5BaCo4O7包含钴离子的 Kagomé 层，其自旋强烈耦合，居里 - 外斯温度为 -2200 K。在低温（T = 1.2 K）下，我们通过极化分析进行的漫中子散射研究揭示了与预测的具有交错手性的二维共面基态相近的特征自旋关联。三维长程反铁磁序的缺失表明 Kagomé 层之间的耦合可忽略不计。散射强度与 Kagomé 层中 Co2+ 的高自旋 S = 3/2 态以及层间位置上 Co3+ 离子的低自旋 S = 0 态一致。我们的观察结果与先前的蒙特卡罗模拟结果相符，表明基态为有效短程、交错手性自旋序。
