Defect-Rich Quasi Two Dimensional Metal Oxides with Strong Ferromagnetism

具有强铁磁性的富缺陷准二维金属氧化物

• 批准号: 2114931
• 负责人: Xudong Wang
• 金额: $ 55万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2114931&HistoricalAwards=false
• 关键词: Defect; Rich; Quasi; Two; Dimensional

Nontechnical DescriptionMaterials that form permanent magnets or are attracted to magnets are called ferromagnetic. Such materials have many uses, ranging from data storage to power systems. However, ferromagnetism is an unusual property that occurs only in a few substances such as iron, nickel, cobalt and their alloys, and some rare earth materials. This project aims to understand how strong ferromagnetism can arise from ultrathin, two-dimensional (2D) materials, that are not magnetic in bulk form. Vacancies, a type of defect arising from “missing” atoms, appear to play a crucial role in stabilizing magnetism in 2D semiconductors. The investigators will perform a combined experimental and theoretical study to determine the concentration of vacancies that can be formed in these nanosheets and quantify how they impact magnetic properties. This research has the potential to realize low-dimensional ferromagnetic materials with a broad range of applications, including memory devices and quantum computing. This project offers opportunities to provide research experiences to underrepresented minority undergraduate and provides education and training on experimental and computation materials research. This project enriches the Informatics Skunkworks to engage undergraduates in research at the interface of data science and materials science and engineering. The research project and results will be integrated into outreach to high school teachers and students.Technical DescriptionThe objective of this project is to understand the formation and stabilization mechanisms of massive cation vacancy concentrations in quasi two-dimensional (2D) transition metal oxides and demonstrate that strong ferromagnetism can be induced in non-ferromagnetic oxides by dimension confinement and point defect engineering. This project is based on an overarching hypothesis that cation vacancies can be created and stabilized at a high level in oxides when their thickness is reduced to the nanometer level, which in turn introduces a strong ferromagnetism to the 2D material. The PIs discovered orders of magnitude enhancement of room temperature ferromagnetism from zinc vacancy-rich 2D ZnO nanosheets. A strong cooperative coupling phenomenon stabilized a vacancy concentration greater than 30% in ZnO nanosheets, enabled by ionic layer epitaxy. The combined experimental and theoretical research project consists of three specific research tasks. Task 1 is a theoretical study to understand the fundamental mechanisms of massive cation vacancy concentration stabilization and associated strong ferromagnetism in 2D oxide lattices. Task 2 is an experimental investigation of zinc vacancy evolution and stabilization mechanisms in ZnO nanosheets to understand the cation vacancy formation and stabilization mechanisms in correlation to the nanoscale thickness, surfaces and grain boundaries. In task 3, the extraordinary magnetic properties rising from the cation vacancies in ultrathin nanosheets are quantified in cerium and manganese oxides, as representative examples to reveal vacancy ordering contribution, and cation vacancy and transition metal moment coupling effects, respectively. Success of this project brings transformative knowledge for the design and synthesis of a new family of ferromagnetic 2D nanomaterials with high magnetization and multi-functionality.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术性描述形成永磁体或被磁体吸引的材料称为铁磁材料。这种材料有许多用途，从数据存储到电力系统。然而，铁磁性是一种不寻常的性质，只出现在少数物质中，如铁，镍，钴及其合金，以及一些稀土材料。这个项目的目的是了解如何强大的铁磁性可以从二维（2D）材料中产生，这些材料在块状形式下没有磁性。空位，一种由“缺失”原子引起的缺陷，似乎在稳定二维半导体的磁性方面起着至关重要的作用。研究人员将进行实验和理论相结合的研究，以确定这些纳米片中可能形成的空位浓度，并量化它们如何影响磁性。这项研究有可能实现具有广泛应用的低维铁磁材料，包括存储设备和量子计算。该项目提供了机会，为代表性不足的少数民族本科生提供研究经验，并提供实验和计算材料研究的教育和培训。该项目丰富了信息学Skunkworks，使本科生能够在数据科学和材料科学与工程的界面上进行研究。该研究项目和结果将被整合到推广到高中教师和学生。技术说明本项目的目标是了解准二维（2D）过渡金属氧化物中大量阳离子空位浓度的形成和稳定机制，并证明通过尺寸限制和点缺陷工程可以在非铁磁性氧化物中诱导强铁磁性。该项目基于一个总体假设，即当氧化物的厚度降低到纳米级时，可以在氧化物中产生并稳定在高水平的阳离子空位，这反过来又为2D材料引入了强铁磁性。研究人员发现，锌空位丰富的2D ZnO纳米片的室温铁磁性增强了几个数量级。一个强大的合作耦合现象稳定的空位浓度大于30%的ZnO纳米片，使离子层外延。实验与理论相结合的研究项目包括三个具体的研究任务。任务1是一个理论研究，以了解大量的阳离子空位浓度稳定和相关的强铁磁性在二维氧化物晶格的基本机制。任务2是ZnO纳米片中锌空位演化和稳定机制的实验研究，以了解与纳米级厚度、表面和晶界相关的阳离子空位形成和稳定机制。在任务3中，在铈和锰氧化物中量化了超薄纳米片中阳离子空位产生的非凡磁性，作为代表性例子，分别揭示了空位有序贡献以及阳离子空位和过渡金属矩耦合效应。该项目的成功为设计和合成具有高磁化强度和多功能性的新型铁磁二维纳米材料家族带来了变革性的知识。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Nucleation Kinetics and Structure Evolution of Quasi-Two-Dimensional ZnO at the Air–Water Interface: An In Situ Time-Resolved Grazing Incidence X-ray Scattering Study

空气-水界面处准二维 ZnO 的成核动力学和结构演化：原位时间分辨掠入射 X 射线散射研究

• DOI: 10.1021/acs.nanolett.2c00300
• 发表时间: 2022
• 期刊: Nano Letters
• 影响因子: 10.8
• 作者: Zhang, Ziyi;Carlos, Corey;Wang, Yizhan;Dong, Yutao;Yin, Xin;German, Lazarus;Berg, Kelvin Jordan;Bu, Wei;Wang, Xudong
• 通讯作者: Wang, Xudong