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: 0856707
• 负责人: Ramki Kalyanaraman
• 金额: $ 26.81万
• 依托单位: University of Tennessee Knoxville
• 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: 2008-07-01 至 2012-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0856707&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）确定激光诱导的自组织在纳米结构和磁各向异性中的外部磁场的作用，以及（2）开发现象学模型，以了解外部依赖效果。 PI将通过综合活动实现这些目标，涉及纳秒激光诱导的自组织，纳米级磁性测量以及这些纳米镜系统中磁化的现象学建模的实验。纳米级磁各向异性的控制促使磁化强度指向所需的方向，可以看作是实现功能性纳米磁性材料的基本要求。到目前为止，磁各向异性主要是通过操纵两个贡献来实现的：（i）各向异性，即具有较大的纵横比结构； （ii）通过晶体学方向或纹理生长通过晶体学方向而各向异性。最近，PIS发现，通过快速激光诱导的自组织产生的近乎近晶的多晶纳米磁体在各个方向上显示出稳定的且尺寸依赖性的磁各向异性。这种行为在所研究的所有磁性材料中普遍存在，包括CO，Ni，Fe和Fe-Co合金。在该项目中，PI通过以下活动来实现对磁各向异性及其在纳米级材料中的控制的基本理解：（i）研究热和单轴菌株和静水压力在快速激光器自组织中的磁各向异性的作用。 （ii）研究外部磁场对磁各向异性，微结构以及成核和生长的作用。 （iii）为快速激光自组织的纳米结构开发了纳米级磁性的现象学模型。这种综合实验和理论活动的智力优点将源于以下特征：（a）这将是探索快速激光自组织，热应变，外部磁场和成核与纳米级磁各向异性上快速激光自组织之间的耦合。这会导致纳米颗粒相图吗？准确地描述了这种耦合以及所得的微结构和磁各向异性。 （b）PI预测新型磁性材料的设计和合成，可能会影响数据存储，传感和信息处理的领域。非技术性：这项活动的更广泛影响将是致力于扩大研究生，本科和高中生的研究和教育经验的承诺。具体影响包括：（a）在包括材料科学，激光材料处理，凝结物理学和磁性的多学科领域的本科生和研究生的培训。 （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能够采用基于设计和发现的计划来综合新材料。 （c）大学和高中生的积极参与（通过辉瑞/Solutia明星计划）将帮助培训具有核心国家利益的纳米科学领域的未来科学家，从而帮助美国在科学和技术方面继续领导。