新型二维磁性材料/铁电氧化物范德华异质结的界面自旋态及其调控研究

低维磁性材料与铁电氧化物组成的异质结可实现室温下低电场对磁性的操控，在未来低功耗自旋电子器件中有广阔的应用前景。在常规的这类异质结中，界面处的强轨道杂化效应非常容易导致氧离子迁移，会对磁性层造成不可逆的破坏，极大制约了器件的使用寿命。为克服这一不利因素，本项目拟采用新型二维磁性材料/铁电氧化物构造范德华异质结，从而弱化界面轨道杂化，以避免磁性层的破坏，并最终克服相关器件的使用寿命问题。围绕着如何基于弱轨道杂化的界面实现强磁电耦合、以及如何实现具有高居里温度的自旋态这两个核心问题，从界面序参量与磁性层自旋态的耦合关联出发，结合实空间第一性原理计算，我们拟建立描述界面自旋态及其耦合的有效哈密顿量。在此基础上，揭示磁电耦合机制，提出增加耦合强度、提高居里温度的可能策略；并探讨界面材料的选择、掺杂，以及施加外场等方法对其界面耦合效应的影响与调控，为低功耗、长使用寿命的自旋器件的设计提供科学依据。

The heterostructure composed of low-dimensional magnetic material and ferroelectric oxide can realize the control of magnetism with low electric field at room temperature, which has great potential application in low-power spintronic devices in the future. However, in the conventional heterostructures, the strong orbital hybridization at the interface can easily induce the migration of oxygen ions and thus results in the irreversible damage to the magnetic layer, which greatly restricts the service life of the device. To overcome this issue, in this project, we propose a new type of the heterostructure based on Van der Waals interaction, which is composed of novel two-dimensional magnetic materials and ferroelectric oxide. The weak orbital hybridization at the interface can efficiently avoid the damage to the magnetic layer and finally overcome the limited service life of the heterostructure devices. To realize the strong magnetoelectric coupling effect and the high Curie temperature of the spin states in such heterostructure, we will first establish an effective Hamiltonian describing the interface spin states as well as the interlayer coupling effects by combining the model Hamiltonian method with the real-space first principles calculations. Then, we will reveal the magnetoelectric coupling mechanism, and propose the possible strategies that can increase the magnetoelectric coupling strength as well as the curie temperature. Finally, we will manipulate the interface effects by changing heterostructure composition, interface doping, and applying external electric field, to realize the strong magnetoelectric coupling property and the high Curie temperature of the interface spin states. Our study is expected to provide a scientific basis for the design of long-life, low-power spintronic devices.