EAGER: Magnetic Nanostructures with Perpendicular Anisotropy

磁性材料的一个关键属性是在某些方向上保持其磁矩的能力，或磁各向异性。例如，一根铁针通常是沿着其长轴磁化的，而一张薄的铁箔的磁矩位于薄膜平面内。然而，某些薄膜形式的纳米级磁体更倾向于将其磁矩垂直于薄膜-称为垂直磁各向异性。这种纳米磁体在技术上非常重要，因为它们可以在更高的密度下实现更有效的信息存储，类似于用小的房地产占地面积建造摩天大楼的好处。 该项目研究了两种类型的具有潜在变革性技术影响的纳米材料：1。铁/铂基材料的有序合金作为下一代高密度磁记录中的存储介质; 2.一种新型的纳米磁体阵列，其中磁矩采取了一种特殊的安排，称为skyrmion状态。磁skyrmions提供了潜在的信息存储新机制，不仅强大，而且能源效率高，预计能源成本仅为当前技术的一小部分。参与的学生将接触到大学，国家实验室和用户设施，以及工业研究和开发的研究经验。有序相的FePt基合金材料由于具有高的各向异性、大的饱和磁化强度和适中的居里温度，是新兴的热辅助磁记录技术的理想介质选择。该项目解决了方便实现高各向异性相，理解和控制开关场分布的关键挑战。研究了有序相的FePt基合金薄膜。磁化反转的基本理解和控制是通过在高温下的磁力测量和一阶反转曲线研究获得的。第二个研究领域集中在表现出拓扑保护量子态和其他独特的拓扑现象的磁skyrmions。合成了基于垂直各向异性薄膜的混合Skyrmion晶格，并研究了室温下的基态。一组磁场序列被用来建立skyrmion晶格，以及涡旋晶格和混合晶格进行比较。磁成像，极化中子反射仪，磁输运研究，和微磁模拟进行探测skyrmion和他们对外界刺激的反应。这些人造skyrmions预计将在很宽的温度和场范围内保持稳定，从而为探索这种奇异自旋纹理中的有趣物理学提供了一个令人兴奋的平台。

Non-Technical AbstractA key attribute of a magnetic material is the ability to retain its magnetic moment in certain directions, or magnetic anisotropy. For example, an iron needle is usually magnetized along its long axis and a thin iron foil would have its moments lying in the film plane. Certain nanoscale magnets in thin film forms, however, prefer to orient their moments perpendicular to the films - known as perpendicular magnetic anisotropy. Such nanomagnets are technologically important, as they allow much more efficient information storage at higher densities, analogous to the benefits of building skyscrapers with small real-estate footprints. This project investigates two types of such nanomaterials that have potentially transformative technological impacts: 1. ordered alloys of iron/platinum-based materials as storage media in next generation ultrahigh density magnetic recording; 2. a novel type of nanomagnet arrays where the magnetic moments take up a special arrangement known as the skyrmion state. The magnetic skyrmions offer potentially new mechanisms for information storage that is not only robust, but also highly energy efficient, expected to be at a tiny fraction of the energy cost of current technologies. Students involved will receive exposure to research experiences in university, national laboratory and user-facility, and industrial research and development. Technical AbstractAlloys of FePt-based materials in the ordered phase are promising media choices for the emerging heat-assisted magnetic recording technology due to their high anisotropy, large saturation magnetization, and moderate Curie temperature. This project addresses critical challenges in the convenient realization of the high anisotropy phase, and understanding and control over the switching field distribution. Thin films of FePt-based alloys in the ordered phase are investigated. Basic understanding and control of the magnetization reversal are gained through magnetometry and first-order reversal curve studies at elevated temperatures. The second research area focuses on magnetic skyrmions that exhibit topologically protected quantum states and other unique topological phenomena. Hybrid skyrmion lattices based on perpendicular anisotropy films are synthesized and investigated to demonstrate the ground state at room temperature. A set of magnetic field sequences is followed to establish the skyrmion lattices, as well as vortex lattices and mixed lattices for comparison. Magnetic imaging, polarized neutron reflectometry, magneto-transport studies, and micromagnetic simulations are carried out to probe the skyrmions and their responses to external stimuli. These artificial skyrmions are expected to be stable over wide temperature and field ranges, thus offering an exciting platform to explore the intriguing physics in such exotic spin textures.