二维多铁异质结中磁电耦合的第一性原理研究

Multiferroic heterostructure is composed of ferroelectric material and magnetic material. It has strong magnetoelectric coupling, which can realize mutual control of electricity and magnetism, so it has important application prospects in high efficiency and low energy consumption storage devices. However, if materials become thinner, traditional three-dimensional ferroelectric materials and magnetic materials are difficult to maintain their original properties when they are close to two-dimensional thickness, making it difficult for three-dimensional multiferroic heterostructures to satisfy the pursuit of smaller memory devices. This project intends to form two types of multiferroic heterostructures with the newly discovered two-dimensional ferroelectric materials and two-dimensional magnetic materials: van der Waals vertical heterostructure and in-plane lateral heterostructure. Calculate the magnetoelectric coupling strength of the two-dimensional systems using the first-principles method, and study how the magnetoelectric coupling mechanism is different from the three-dimensional systems, and explore the reasonable means of enhancing the magnetoelectric coupling through external conditions such as strain and doping. Based on the results of these studies, we can design a two-dimensional multiferroic heterostructure with strong magnetoelectric coupling. The research of this project can enrich the understanding of magnetoelectric coupling and is of great significance for realizing memory devices close to the thickness of single atomic layer.

由铁电材料与磁性材料拼接组成的多铁异质结中存在较强的磁电耦合，可以实现电和磁的互相调控，因此在高效率、低能耗的存储器件中有重要的应用前景。然而随着材料变薄，传统的三维铁电材料与磁性材料在接近二维厚度时很难保持原本的性质，这让三维多铁异质结很难满足人们对更小型存储器件的追求。本项目拟通过第一性原理计算的手段，用最新发现的二维铁电材料与二维磁性材料组成两类多铁异质结：范德瓦尔斯垂直异质结与面内横向异质结，计算这两种二维体系的磁电耦合强度，研究其磁电耦合机制与三维体系相比有什么不同，并通过应变、掺杂等外部条件变化来探索增强磁电耦合的合理手段，从而设计具有强磁电耦合的二维多铁异质结。本项目的研究，能够丰富对磁电耦合的理解，对实现接近单原子层厚度的存储器件具有重要意义。

同时具有铁电性与铁磁性的材料往往具有磁电耦合的性质，可以实现电和磁的相互调控，在高效率、低能耗的存储器等自旋电子学器件中有重要应用，然而，铁电性与磁性对材料外层电子排布的要求不同，使得多铁材料的种类十分有限。此外，传统的三维材料在接近二维厚度时很难保持原有的铁电性与磁性，从而难以满足人们对器件小型化的诉求。本项目通过第一性原理计算的手段，提出了设计二维多铁材料的一种方法：在具有特殊电子结构的二维铁电材料中通过载流子掺杂或原子缺陷来引入Stoner巡游铁磁性，从而实现二维多铁性。之后，我们重点研究了二维系统中磁电耦合的强度、产生机制与调控手段，发现了一种内建电场机制下的表面磁电耦合效应，这种磁电耦合还可以出现在一维系统中。最后，我们还研究了二维磁性系统中的磁性、拓扑性与能谷特性的调控与相互作用。我们的研究丰富了对磁电耦合的理解，对实现微型自旋电子学器件提供了帮助。