二维磁性材料：高通量筛选

磁性材料，特别是铁磁半导体，可以与现代半导体工艺进行集成，因此往往被认为是自旋电子学领域中的理想材料。除了本征磁性半导体外，过渡金属掺杂的稀磁半导体也得到广泛研究。另外，不含d/f电子的室温d0铁磁半导体也是磁性材料研究的一个重要分支。由于空穴媒介作用被认为是“d0铁磁性”的起源，且可以通过掺杂甚至缺陷来实现，这种“d0铁磁性”为寻找高温自旋电子材料提供了不同的方案与可能性。与此同时，在过去十年里，二维本征铁磁材料也快速发展，甚至已有一些自旋隧道结的测量研究。

Fig. 1 The workflow of the high-throughput screening for 2D hole-doping induced ferromagnetic materials.

然而，二维本征铁磁材料十分缺乏，且它们普遍拥有较低的居里温度，不利于低维自旋电子学器件的发展与应用。近年来研究者逐渐将目光移至掺杂诱导的二维d0铁磁半导体，但是系统的研究依旧缺乏，且自旋极化空穴的交换耦合与非局域化机制尚不清晰。

Fig. 2 Overview of the representative atomic structures of the 2DHDFM, sorted by chemical compositions and space groups.

来自荷语鲁汶大学物理天文学院的Ruishen Meng教授与Michel Houssa教授合作，从三个主流数据库中筛选了数千个二维非磁半导体，并借助高通量密度泛函理论计算，确定出了空穴掺杂引起磁性的潜在候选材料。

Fig. 3 Distribution of spin-polarization energies, magnetic anisotropic energies (MAE) per magnetic ion and magnetic exchange interaction parameters of the 2DHDFM.

他们对材料进行了稳定性计算，最终确定出122种稳定的二维材料。这些材料均可以由空穴掺杂实现稳定的磁有序，并且部分体系的居里温度达到了室温。最后，他们还讨论了铁磁有序的交换相互作用。

Fig. 4 Distribution of Curie temperatures of the 2DHDFM.

该工作大大丰富了二维磁性材料库，同时对空穴掺杂诱导铁磁材料提供了一定的理论见解，为将来实现二维自旋电子器件打下了一定基础。相关论文近期发布于npj Computational Materials 8: 230 (2022)。

Fig. 5 Spin densities and orbital projected density of states of the selected 2DHDFM.

Editorial Summary

2D magnetic materials: High-throughput screening

Magnetic materials, especially ferromagnetic semiconductors, are considered advantageous in the field of spintronics because of their easy integration into semiconductor devices. Apart from the intrinsic magnetic materials, research attention has also been focusing on dilute magnetic semiconductors (DMSs). Besides, room temperature d0FM semiconductor without d/f electrons is also an important branch of magnetic materials. As hole mediation is considered to be the origin of the ‘d0ferromagnetism’, which can be realized by acceptor doping or even by intrinsic defects, the ‘d0 ferromagnetism’ offers a different way and possibility to hunt for high-temperature spintronic materials. Meanwhile, the past decade has witnessed the rapid development of 2D magnetic materials and even 2D tunneling junctions. However, the scarcity of 2D FM semiconductors and their rather low Curie temperature (Tc) hamper practical applications as well as the further investigation of 2D magnetism. In the recent years, studies have predicted several (hole-)doping induced 2D d0 FM semiconductors. However, a systematic investigation of the magnetic properties of these 2D materials is still lacking. The mechanism responsible for the exchange coupling and delocalization of the spin-polarized holes has not been discussed yet.

Fig. 6 Schematic diagram of the magnetic exchange interactions.

A team led by Prof. Ruishen Meng and Prof. Michel Houssa from the Department of Physics and Astronomy in KU Leuven Celestijnenlaan 200D, screened thousands of 2D non-magnetic semiconductors/insulators from three databases, and performed a high-throughput density functional theory calculation to identify potential 2D FM materials induced by hole doping. They then verified the stability of the potential candidates, for which 122 materials were recognized as stable 2D FM materials upon hole doping. The computed Curie temperatures of some systems were close to or above room temperature. At last, the exchange interaction mechanisms responsible for the FM coupling in these 2D materials were also discussed. This work not only provides theoretical insights into hole-doped 2D FM materials, but also enriches the family of 2D magnetic materials for possible spintronic applications, laying a certain foundation for the realization of two-dimensional spintronic devices in the future. This article was recently published in npj Computational Materials 8: 230 (2022).

原文Abstract机器翻译

Hole-doping induced ferromagnetism in 2D materials (空穴掺杂诱导二维材料铁磁性)
Ruishen Meng, Lino da Costa Pereira, Jean-Pierre Locquet, Valeri Afanas’ev, Geoffrey Pourtois & Michel Houssa

Abstract Two-dimensional (2D) ferromagnetic materials are considered as promising candidates for the future generations of spintronic devices. Yet, 2D materials with intrinsic ferromagnetism are scarce. Hereby, high-throughput first-principles simulations are performed to screen 2D materials that present a non-magnetic to a ferromagnetic transition upon hole doping. A global evolutionary search is subsequently performed to identify alternative possible atomic structures of the eligible candidates, and 122 materials exhibiting a hole-doping induced ferromagnetism are identified. Their energetic and dynamic stability, as well as magnetic properties under hole doping are investigated systematically. Half of these 2D materials are metal halides, followed by chalcogenides, oxides, and nitrides, some of them having predicted Curie temperatures above 300 K. The exchange interactions responsible for the ferromagnetic order are also discussed. This work not only provides theoretical insights into hole-doped 2D ferromagnetic materials, but also enriches the family of 2D magnetic materials for possible spintronic applications.

摘要 二维（2D）铁磁材料是未来建构自旋电子器件有前途的候选材料。然而，具有本征铁磁性的二维材料相当稀缺。在此，通过高通量第一性原理模拟，我们筛选出了一系列二维材料，它们会在空穴掺杂条件下呈现出非磁性到铁磁序的转变。随后，我们进行了全局演化搜索其他可能的结构，最终确定了122种表现出空穴掺杂诱导铁磁性的二维材料。我们系统地研究了它们在掺杂时的能量和动力学稳定性以及磁学性质。这些二维材料有一半是金属卤化物，其次是硫族化合物、氧化物和氮化物，其中一些材料的居里温度可以超过300 K。我们还讨论了铁磁序相关的交换相互作用。这项工作不仅为空穴掺杂的二维铁磁材料提供了理论见解，而且大大丰富了二维磁性材料家族，有望实现自旋电子器件应用。