Kang Seungjin, Yu Jaejun
Center for Theoretical Physics, Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea.
Phys Chem Chem Phys. 2022 Sep 21;24(36):22168-22180. doi: 10.1039/d2cp02612k.
Kagome metal-organic frameworks (MOFs) are considered a new class of materials that can host two-dimensional (2D) magnetism and correlated electron phenomena such as superconductivity and quantum anomalous Hall effect. Despite its potential for spintronics applications and others, the systematic understanding between the electronic structure and magnetic properties of kagome MOFs is still missing. This work determines the crystal structure, magnetic ground states, and anisotropy of a series of transition metal atoms and ligands from first-principles calculations. We reveal that the coexistence of covalent and ionic bonding characters of 3d orbitals is a distinctive feature of the 2D kagome MOFs. Furthermore, we demonstrate that the occupancies of active bands near the Fermi level are responsible for different superexchange mechanisms: the partially filled bands with empty for V and Co MOFs lead to antiferromagnetic ordering, and the partially filled bands with full for Mn, Fe, and Co MOFs lead to ferromagnetic ordering between transition metal ions. It is pointed out that the bands are formed through dpπ-hybridization between the transition metal d, d and ligand p orbitals in the square planar coordination of metal atoms. This mechanism provides valuable insights into understanding magnetism in 2D kagome MOFs.
戈薇金属有机框架（MOFs）被认为是一类新型材料，能够承载二维（2D）磁性以及诸如超导和量子反常霍尔效应等关联电子现象。尽管其在自旋电子学应用及其他方面具有潜力，但戈薇MOFs的电子结构与磁性之间的系统理解仍然缺失。这项工作通过第一性原理计算确定了一系列过渡金属原子和配体的晶体结构、磁基态和各向异性。我们揭示出3d轨道的共价和离子键特征共存是二维戈薇MOFs的一个显著特征。此外，我们证明费米能级附近活性带的占据情况导致了不同的超交换机制：V和Co MOFs中部分填充带且有空位导致反铁磁有序，而Mn、Fe和Co MOFs中部分填充带且已满则导致过渡金属离子之间的铁磁有序。指出这些能带是通过金属原子平面四方配位中过渡金属d、d和配体p轨道之间的dpπ杂化形成的。这种机制为理解二维戈薇MOFs中的磁性提供了有价值的见解。
