Chen Dong, Zhang Guangbiao, Cheng Zhenxiang, Dong Shuai, Wang Yuanxu
Institute for Computational Materials Science, School of Physics and Electronics, Henan University, Kaifeng 475000, People's Republic of China.
Institute for Superconducting and Electronic Materials, Australian Institute of Innovative Materials, University of Wollongong, Wollongong NSW 2500, Australia.
IUCrJ. 2019 Jan 15;6(Pt 2):189-196. doi: 10.1107/S205225251801624X. eCollection 2019 Mar 1.
Robust control of magnetism is both fundamentally and practically meaningful and highly desirable, although it remains a big challenge. In this work, perovskite oxide superstructures LaFeO/BaTiO (LFO/BTO), LaMnO/BaTiO (LMO/BTO) and LaCrO/BaTiO (LCO/BTO) (001) are designed to facilitate tuning of magnetism by the electric field from ferroelectric polarization, and are systemically investigated via first-principles calculations. The results show that the magnetic ordering, conductivity and exchange interactions can be controlled simultaneously or individually by the reorientation of the ferroelectric polarization of BTO in these designed superstructures. Self-consistent calculations within the generalized gradient approximation plus on-site Coulomb correction did not produce distinct rotations of oxygen octahedra, but there were obvious changes in bond length between oxygen and the cations. These changes cause tilting of the oxygen octahedra and lead to spin, orbital and bond reconstruction at the interface, which is the structural basis responsible for the manipulation. With the G-type antiferromagnetic (G-AFM) ordering unchanged for both ± cases, a metal-insulator transition can be observed in the LFO/BTO superstructure, which is controlled by the LFO thin film. The LMO/BTO system has A-type antiferromagnetic (A-AFM) ordering with metallic behavior in the + case, while it shifts to a half-metallic ferromagnetic ordering when the direction of the polarization is switched. LCO/BTO exhibits C-type antiferromagnetic (C-AFM) and G-AFM orders in the + and - cases, respectively. The three purpose-designed superstructures with robust intrinsic magnetoelectric coupling are a particularly interesting model system that can provide guidance for the development of this field for future applications.
尽管对磁性进行稳健控制仍然是一个巨大的挑战，但它在基础研究和实际应用中都具有重要意义且备受期待。在这项工作中，设计了钙钛矿氧化物超结构LaFeO/BaTiO（LFO/BTO）、LaMnO/BaTiO（LMO/BTO）和LaCrO/BaTiO（LCO/BTO）（001），以通过铁电极化产生的电场促进对磁性的调控，并通过第一性原理计算进行了系统研究。结果表明，在这些设计的超结构中，BTO铁电极化的重新取向可以同时或分别控制磁有序、电导率和交换相互作用。在广义梯度近似加上在位库仑校正下的自洽计算没有产生氧八面体的明显旋转，但氧与阳离子之间的键长有明显变化。这些变化导致氧八面体倾斜，并在界面处导致自旋、轨道和键的重构，这是实现操控的结构基础。在±两种情况下，G型反铁磁（G-AFM）有序均保持不变，在LFO/BTO超结构中可以观察到由LFO薄膜控制的金属-绝缘体转变。LMO/BTO系统在+情况下具有A-型反铁磁（A-AFM）有序和金属行为，而当极化方向切换时，它转变为半金属铁磁有序。LCO/BTO在+和-情况下分别表现出C型反铁磁（C-AFM）和G-AFM有序。这三个经过专门设计的具有强大本征磁电耦合的超结构是一个特别有趣的模型系统，可为该领域未来应用的发展提供指导。
