| 报告题目 | Magnetic and crystal structures of the honeycomb-lattice Na2IrO3 and square-lattice Sr2IrO4 |
| 报告人 | 叶峰 博士 |
| 报告人单位 | 美国橡树岭国家实验室 |
| 报告时间 | 2013-05-21 |
| 报告地点 | 合肥微尺度物质科学国家实验室九楼会议室 |
| 主办单位 | 合肥微尺度物质科学国家实验室 |
| 报告介绍 | 报告摘要： 5d based iridates have recently attracted great attention due to the large spin-orbit coupling (SOC). It is now recognized that the SOC that competes with other relevant energies, particularly the on-site Coulomb interaction U, and have driven novel electronic and magnetic phases. Combining single crystal neutron and x-ray diffractions, we have investigated the magnetic and crystal structures of the honeycomb lattice Na2IrO3 and square lattice Sr2IrO4. For Na2IrO3, the system orders magnetically below 18.1 K with Ir4+ ions forming zigzag spin chains within the layered honeycomb network. Such a configuration sharply contrasts the Neel or stripe states proposed in the Kitaev-Heisenberg model. The structure refinement reveals that the Ir atoms form nearly ideal 2D honeycomb lattice while the IrO6 octahedra experience a trigonal distortion that is critical to the ground state. For Sr2IrO4, we revealed that the spin orientation rigidly tracks the staggered rotation of the IrO6 octahedra. The long-range antiferromagnetic order has a canted spin configuration. The forbidden nuclear reflections of space group I41/acd are also observed and suggest a reduced crystal structure symmetry. The results of our study provide much-needed experimental insights into the magnetic and crystal structure crucial to the understanding of the exotic magnetic order in the 5d-electron based materials. |
