Zhou Hai Yang, Chen Xiang Ming
Laboratory of Dielectric Materials, School of Materials Science and Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027, People's Republic of China.
J Phys Condens Matter. 2017 Apr 12;29(14):145701. doi: 10.1088/1361-648X/aa5e3e. Epub 2017 Feb 27.
The structural distortions, orbital ordering, magnetic and electronic properties of double perovskite RCoMnO (R = rare-earth element) have been systematically calculated by first-principles. Structural distortions, including Co-O and Mn-O bond length splitting, the antiferroelectric motions of R ions, the tilting of octahedral (the resulted Co-O-Mn bond angle) are obviously affected by the rare-earth ions' radius. The bond length splitting behavior of Co-O and Mn-O are rather different because of the Jahn-Teller active ion Co and the Jahn-Teller nonactive ion Mn. Taking GdCoMnO as an example, the t orbitals of Co ions are predicted to be orbital ordered. That is, the spin down channel of d orbital for one Co ion and d orbital for another Co ion are basically vacant. Finally, the physical properties, including the magnetic Curie temperature and electronic band gap of RCoMnO are almost linear dependent on the average value of cos θ (θ is the Co-O-Mn exchange-angle).
通过第一性原理系统地计算了双钙钛矿RCoMnO（R =稀土元素）的结构畸变、轨道有序性、磁性和电子性质。结构畸变，包括Co-O和Mn-O键长分裂、R离子的反铁电运动以及八面体的倾斜（导致的Co-O-Mn键角）明显受到稀土离子半径的影响。由于Jahn-Teller活性离子Co和Jahn-Teller非活性离子Mn，Co-O和Mn-O的键长分裂行为有很大不同。以GdCoMnO为例，预测Co离子的t轨道是轨道有序的。也就是说，一个Co离子的d轨道的自旋向下通道和另一个Co离子的d轨道基本上是空的。最后，RCoMnO的物理性质，包括居里温度和电子带隙，几乎与cosθ（θ是Co-O-Mn交换角）的平均值呈线性相关。
