Magnetic Anisotropy in Nanoscale Systems Produced by Fast Laser Processing: Fundamental Mechanisms, Control and Novel Magnetic Materials

快速激光加工产生的纳米级系统中的磁各向异性：基本机制、控制和新型磁性材料

• 批准号: 0805258
• 负责人: Ramki Kalyanaraman
• 金额: $ 27万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-06-15 至 2008-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0805258&HistoricalAwards=false
• 关键词: Magnetic; Anisotropy; Nanoscale; Systems; Produced

TECHNICAL: The objectives of this high-risk exploratory research are (1) To determine the role of external magnetic field during laser-induced self-organization on the nanostructure and magnetic anisotropy and (2) To develop a phenomenological model to understand the external field dependent effects. PIs will realize these goals through an integrated activity involving experiments of nanosecond laser-induced self-organization, measurement of nanoscale magnetism, and phenomenological modeling of magnetization in these nanoscopic systems. The control of nanoscale magnetic anisotropy, which prompts the magnetization to point in desired directions, can be viewed as a fundamental requirement towards realizing functional nanomagnetic materials. Thus far, magnetic anisotropy has been realized primarily through the manipulation of two contributions: (i) shape anisotropy, i.e. with large aspect ratio structures; and (ii) magnetocrystalline anisotropy via crystallographic orientation through epitaxy or textured growth. Recently, PIs have discovered that near-hemispherical polycrystalline single-domain nanomagnets created by fast laser-induced self-organization show stable and size-dependent magnetic anisotropy in various directions. This behavior was universally present in all magnetic materials investigated, including Co, Ni, Fe and an Fe-Co alloy. In this project, PIs aim to achieve a fundamental understanding of magnetic anisotropy and its control in nanoscale materials through the following activities: (i) Investigate the role of thermal and uniaxial strain, and hydrostatic pressure on magnetic anisotropy in fast laser self-organized nanoparticles. (ii) Investigate the role of external magnetic field on magnetic anisotropy, microstructure, and nucleation and growth. (iii) Develop a phenomenological model of nanoscale magnetism for fast laser self-organized nanostructures. The intellectual merit of this integrated experimental and theoretical activity will stem from the following features: (a) This will be the first definitive work exploring the coupling between fast laser self-organization, thermal strain, external magnetic field and nucleation and growth on nanoscale magnetic anisotropy. This will result in ?nanoparticle phase diagrams? that accurately describe this coupling and the resulting microstructure and magnetic anisotropy. (b) PIs anticipate the design and synthesis of novel magnetic materials that could impact areas of data storage, sensing and information processing. NON-TECHNICAL: The broader impact from this activity will be through commitments to broadening research and education experiences of graduate, undergraduate and high-school students. Specific impacts include: (a) The training of undergraduate and graduate students in a multidisciplinary area comprising materials science, laser-materials processing, condensed matter physics and magnetism. (b) The phenomenological model developed through this activity could permit researchers and innovators to undertake a design and discovery based program to synthesize new materials. (c) Active participation of university and high-school students (through the Pfizer/Solutia STARS program) will help train future scientists in the area of nanoscience, which is of core national interest, and thereby help the US continue its leadership in science and technology.

技术：这项高风险探索性研究的目标是(1)确定激光诱导自组织过程中外加磁场对纳米结构和磁各向异性的作用，以及(2)建立一个唯象模型来理解外场依赖效应。PIS将通过一项综合活动来实现这些目标，包括纳秒激光诱导的自组织实验，纳米尺度磁性的测量，以及这些纳米系统中磁化的唯象模型。控制纳米尺度的磁各向异性，促使磁化强度指向所需的方向，是实现纳米功能磁性材料的基本要求。到目前为止，磁各向异性主要是通过两个方面的作用实现的：(I)形状各向异性，即具有大长宽比结构；(Ii)通过外延或织构生长的晶体取向实现磁晶各向异性。最近，PI发现由快激光诱导自组织产生的近半球多晶单畴纳米磁体在不同方向上表现出稳定的、大小相关的磁各向异性。这一行为普遍存在于所研究的所有磁性材料中，包括Co、Ni、Fe和Fe-Co合金。在这个项目中，PI旨在通过以下活动实现对纳米材料中磁各向异性及其控制的基本了解：(I)研究快速激光自组织纳米颗粒中热应变和单轴应变以及静水压力对磁各向异性的作用。(Ii)研究外加磁场对磁各向异性、微观结构以及形核和生长的影响。(3)发展了快激光自组织纳米结构的纳米尺度磁性唯象模型。这一综合的实验和理论活动的智力价值将来自以下特征：(A)这将是第一个探索快速激光自组织、热应变、外部磁场与纳米尺度磁各向异性形核和生长之间的耦合的决定性工作。这会产生纳米颗粒相图吗？准确地描述了这种耦合以及由此产生的微结构和磁各向异性。(B)个人投资项目预期设计和合成可能对数据存储、传感和信息处理领域产生影响的新型磁性材料。非技术性：这项活动的更广泛影响将是通过承诺拓宽研究生、本科生和高中生的研究和教育经验。具体影响包括：(A)在包括材料科学、激光材料加工、凝聚态物理和磁学在内的多学科领域对本科生和研究生进行培训。(B)通过这项活动开发的现象学模型可以使研究人员和创新者开展一项以设计和发现为基础的方案，以合成新材料。(C)大学生和高中生的积极参与(通过辉瑞/首诺之星计划)将有助于培训纳米科学领域的未来科学家，这是国家核心利益，从而帮助美国继续保持其在科学和技术方面的领导地位。