具有大磁各向异性能的合金团簇的计算设计

Magnetic anisotropy energy (MAE) is defined as the energy difference between different magnetization orientations for a magnetic particle, which inhabits lose of the recorded magnetic information under environmental temperature and is the key physical parameter for miniaturization of magnetic information storage. Previous studies have demonstrated that transition metal clusters usually possess much higher MAE per atom than the bulk solid and are promising for magnetic information storage. Controlling the size, geometry and chemical composition of cluster as well as utilizing the cluster-substrate interaction are the effective ways to tune the magnetic anisotropy energy of a cluster. However, the previous works were restricted in the elementary clusters and bimetallic clusters with very narrow range of composition and size. Meanwhile, the choice of two-dimensional substrates was also focused on perfect graphene or graphene with vacancy defects. Based on our previous studies of clusters and two-dimensional materials, here we propose to perform high-throughput computation of alloy clusters with a wider range of composition and size in order to search clusters with large MAE. We will also try graphene and its derivatives as well as two-dimensional organic materials as substrates to stabilize the magnetic cluster and enhances its magnetic anisotropy via cluster-substrate interaction. Eventually, we will be able to design some free and supported alloy clusters with strong magnetic anisotropy, which can be used as ideal building blocks for high-density permanent magnetic storage materials and spintronics devices.

磁各向异性能（MAE）定义为磁性颗粒的磁矩沿着不同磁化方向之间的能量差，它保证了颗粒记录的磁信息在环境温度下不丢失，是磁信息存储小型化的关键物理参数。现有的研究表明：过渡金属团簇通常具有远高于固体的单原子MAE值，在高密度磁存储领域有诱人的应用前景。改变团簇的尺寸、构型、化学成分，利用团簇-衬底相互作用都是调控团簇磁各向异性能的有效手段。然而，现有的研究主要限于单质团簇或双金属团簇，化学成分和尺寸范围均非常有限；二维衬底的选取也集中在完美或含空位缺陷的石墨烯。申请人基于在团簇和二维材料领域的工作基础，提出对较宽成分和尺寸范围的合金团簇开展第一性原理高通量计算搜索，筛选具有较大MAE的团簇；尝试石墨烯、石墨烯衍生物和有机二维材料衬底，通过团簇-衬底相互作用稳定团簇、增强磁各向异性。最终设计出具有强磁各向异性的自由和支撑合金团簇体系，为高密度永磁存储材料和自旋电子学器件提供理想的构造单元。

磁各向异性能（MAE）定义为磁性颗粒的磁矩沿着不同磁化方向之间的能量差，它保证了颗粒记录的磁信息在环境温度下不丢失，是磁信息存储小型化的关键物理参数。本项目面向磁存储材料和自旋电子学器件持续小型化的发展需求，通过自主发展的“第一性原理+遗传算法”CGA程序开展计算搜索，探索调控团簇磁性的内在规律，设计具有强磁各向异性的自由或支撑合金团簇，以及二维金属有机骨架，取得的主要研究进展包括：系统研究了小尺寸Ir团簇的MAE的尺寸演化规律；进一步通过卤素原子调控提升Ir2团簇的MAE，其中Ir2Br的MAE高达294 meV，是目前文献报道几乎最高的理论值；研究了环戊二烯基(Cp)内夹5d过渡金属原子形成的一系列5d金属茂合物分子，在Ta2Cp3中获得了超过60 meV的MAE；系统研究了各类二维金属有机骨架的MAE，包括5d过渡金属修饰二维肽箐骨架、化学功能化5d金属修饰二维卟啉骨架、二维金属有机Kagome晶格、（应变下）开壳层5d过渡金属原子与苯三甲腈构成的二维有机金属骨架，金属原子的最高MAE达到120 meV。研究成果被Nature Research微博等科技媒体进行了新闻报道。通过本项目的研究，在微观上加深对金属原子/团簇磁各向异性能调控机制的认识，为低维永磁存储材料和自旋电子学器件设计，提供前瞻性的理论指导。项目研究团队在Progress in Materials Science，Science Advances（2篇），ACS nano（2篇），Materials Horizons，Advanced Science，Journal of Physical Chemistry Letters（3篇），Nanoscale Horizons（3篇），Applied Physics Letters等本领域重要期刊上发表49篇SCI论文，被引用531次；项目负责人做国际会议邀请报告12次。项目组获教育部自然科学二等奖、辽宁省自然科学二等奖。项目负责人入选长江学者特聘教授、万人计划领军人才，获国务院政府特殊津贴；骨干成员1人入选人社部高层次留学回国人才。项目组培养了13名研究生获博士学位，其中2人获辽宁省优博士论文奖，3人获校优博士论文。