Two-Dimensional Magnetic Materials for the Next Generation of Functional Device Platforms (2DMagnete)

磁性可能是已知的最古老的完全由量子力学起源的物理现象。从William吉尔伯特在他1600年的专著De Magnete中进行的早期研究，到目前使用自旋电子学概念的磁体硬盘驱动器技术，在真正的二维（2D）磁体上仍然存在一些悬而未决的问题。这是一个内在的问题，早在70多年前，该领域的先驱者，如Louis Néel、Lev朗道或Lars Onsager就指出了这一点，但仍然没有一个合理的解决方案。如今，随着不同的计算模拟技术和实验方法的出现，我们有机会在真实的生活基础上解决这个具有基础和技术影响的尖端问题。2017年在单层半导体晶体（如CrI 3）中发现二维磁性和观察层相关磁性相（如反铁磁或铁磁）方面的突破为基础科学和器件技术开辟了新的范式。这些化合物在磁电子学方面具有巨大的潜力，并将逻辑和存储器结合起来用于高性能计算。一个改变游戏规则的想法是将集成的2D磁体开发到选定的矩阵中，作为具有定制功能的智能混合体。这种轻质材料将在电磁干扰屏蔽（例如减少电磁污染），低能耗数据存储（例如更好的硬盘驱动器）和超低功耗开关（例如更智能的健康监测传感器）方面具有变革性的应用。它们的原子薄性质也将使前所未有的操纵磁性能的非磁性手段，如通过电场或机械应变。这些磁体的货车德瓦耳斯（vdW）性质使得能够任意设计异质结和器件，而没有晶格匹配约束，在不同磁体之间或磁体与其他2D材料之间形成。根据诺贝尔奖获得者安德烈·K. Geim，“可能的vdW结构的选择仅受我们想象力的限制”。因此，结合界面工程能力的2D磁体的发现在磁性的基础上开辟了新的天地，具有前所未有的控制和新的功能。在这个项目中，我们将：（1）提出重点理论发展，以阐明器件平台突破性进展的内在vdW材料的磁性。这是由终极问题引发的：“原子层材料的磁性极限是什么，如何操纵它？”“长期以来一直在寻找但最近才发现的真正的2D磁性材料可以使信息数据的访问，理解和存储方式发生革命。他们是如何工作的完全未知。我们的目标是展示这种现象是如何发生的，以及如何控制它，这样做将在有限温度下跨越不同长度尺度的差距，这是一种全新的磁性材料。这将导致对低维磁体的理解的科学突破，以及在超紧凑自旋电子学中以廉价可行的方式将其与光学和电子学集成。(2)要做到这一点，我们有三个步骤：i）开发和应用高通量技术的量子力学模拟，以预测最好的材料，可以真正的二维磁体在温度的技术相关性; ii）在不同的维度上对我们的建模进行基准测试-原子性的（很少的），介观（几nm）和宏观（数百微米）-桥接2D处的磁现象的修改;最后，iii）研究磁性与外部驱动力（电/磁、应变、界面）之间的相互作用，以使用多尺度方法获得磁性控制。从技术上讲，我们的建议将为2D磁体的材料设计铺平道路，并远远超出目前可能的磁性设备上的数据存储应用。

Magnetism is perhaps the oldest known physical phenomenon of entirely quantum mechanical origin. From the early studies performed by William Gilbert in his 1600 monograph De Magnete, through to current magnet hard-drive technology using spintronics concepts, several open questions still remain on the limit of magnetism at truly two-dimensional (2D) magnets. This is an intrinsic problem pointed out more than 70 years ago by pioneers in the field such as Louis Néel, Lev Landau or Lars Onsager but still without a plausible solution. Nowadays with the advent of different computational simulation techniques, and experimental approaches, we have the opportunity to tackle this cutting-edge problem with fundamental and technological implications in a real live-basis. The 2017 breakthroughs in discovery of 2D magnetism in monolayer semiconductor crystals (e.g. CrI3) and observation of layer-dependent magnetic phases (e.g. antiferromagnetic or ferromagnetic) open up new paradigms in fundamental science and device technologies. These compounds have enormous potential for magneto-electronics, as well as combining logic and memory for high-performance computing. One game-changing idea is to develop integrated 2D-magnets into selected matrices as smart hybrids with tailored functionalities. Such lightweight materials will have transformative applications in electromagnetic interference shielding (e.g. reduce electromagnetic pollution), low-energy data storage (e.g. better hard-drives), and ultralow-power switching (e.g. smarter health monitoring sensors). Their atomically thin nature will also enable unprecedented manipulation of magnetic properties by non-magnetic means, such as via electric fields or mechanical strain. The van der Waals (vdW) nature of these magnets enables arbitrary design of heterojunctions and devices, without lattice-matching constraints, formed either between different magnets or between magnets and other 2D materials. According to Nobel laureate Andre K. Geim, "the choice of possible vdW structures is limited only by our imagination". Thus, the discovery of 2D magnets combined with interfacial engineering capabilities breaks new ground in the fundamentals of magnetism, with unprecedented control and new functionality. In this project we will: (1) propose focused theory developments to elucidate the magnetic properties of intrinsic vdW materials to groundbreaking advances in device platforms. This is triggered by the ultimate question: "What is the limit of magnetism in an atomic layer material and how to manipulate it?" Long-searched but only recently discovered, truly 2D magnetic materials could enable a revolution on how information data is accessed, understood and stored. How they work is completely unknown. We aim to show how this phenomenon occurs and how to control it. Doing so would bridge the gap across different length scales at finite temperature of a radical new class of magnetic materials. This will lead to a scientific breakthrough in the understanding of low-dimensional magnets and their integration with optics and electronics in a cheap and feasible way in ultra-compact spintronics. (2) To do this we have three steps to take: i) to develop and apply high-throughput techniques to quantum mechanical simulations to predict the best materials that can be truly 2D magnets at temperatures of technological relevance; ii) to benchmark our modelling across different dimensionalities - atomistic (few Å's), mesoscopic (several nm's) and macroscopic (hundreds of micrometer's) - to bridge the modifications of the magnetic phenomena at 2D; and, finally, iii) to investigate the interplay between magnetic properties with external driving forces (electric/magnetic, strain, interfaces) to obtain magnetic control using multiscale methods. Technologically, our proposal would pave the way to materials design of 2D-magnets and goes well beyond the currently possible applications of data storage on magnetic device.