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

点击翻译按钮获取中文摘要

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.