SGER: Realization of Half-Metallicity in Magnetite

SGER：磁铁矿中半金属丰度的实现

• 批准号: 0852862
• 负责人: Jinke Tang
• 金额: $ 17.06万
• 依托单位: University of Wyoming
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-11-15 至 2010-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0852862&HistoricalAwards=false
• 关键词: SGER; Realization; Half; Metallicity; Magnetite

TECHNICAL: While attractive to many, true half-metals have not been observed experimentally. The room temperature value of the spin polarization falls far short of 100% for all theoretically predicted half-metals. The experimentally reported room temperature spin polarization of Fe3O4 varies between 20 and 80%. Several factors may contribute to the lack of metallicity, including surface oxidation and reconstruction, presence of magnons, surface magnetic state being different from the bulk, and the properties of the barrier materials when the experiments involve magnetic tunneling junctions. In this project, an innovative and exploratory approach to unveil the spin polarization of Fe3O4 is to be investigated. Ultra thin oxygen-free organic overlayers will be applied to the surfaces of Fe3O4 to prevent its oxidation and to lift the reconstruction with the ultimate goal of restoring the true spin polarized nature on its surfaces. Understanding that achieving 100% spin polarization may be difficult, this investigation also aims at the realization the highest possible half-metallicity in Fe3O4. Both high quality epitaxial films and cleaved surfaces of single crystal Fe3O4 will be prepared. A group of organic overlayers that show promise for the stated purposes, including styrene, thiols, graphene and carbon ?dusting?, will be deposited on the surfaces. The chemical and structural properties and spin polarization of the surfaces with/without overlayers will be investigated with state-of-the-art characterization tools and magnetic tunnel junctions will be made for additional spin polarization measurements. Due to the unavoidable presence of the surface states that are different from the bulk, it has been an extremely difficult task to probe the true spin polarization of Fe3O4. The project points to a novel and promising way to overcome such obstacle by applying overlayers on various surfaces of Fe3O4. Such efforts to protect the surfaces from oxidation and, in particular, to lift the reconstruction have not been tested before, and the risk is high in terms of the outcome of the project. However, the potential impact will be tremendous as it leads to a completely new and transformative approach to reveal the bulk spin-resolved electronic properties. NON-TECHNICAL: If successful, realizing half-metallicity in Fe3O4 will be groundbreaking to the spintronic materials research and will have a huge impact on the science and technology of spintronics. This high risk high payoff project should have a direct economic impact on the future information technology. Both graduate and undergraduate students, especially underrepresented minorities and females, will be provided with training opportunities in condensed matter physics and materials science that are strongly linked to advanced technology.

技术：虽然对许多人有吸引力，但真正的半金属还没有在实验中观察到。自旋极化福尔斯的室温值远远低于100%的所有理论预测的半金属。实验报告的室温自旋极化的Fe 3 O 4之间变化20和80%。有几个因素可能导致金属性的缺乏，包括表面氧化和重建，磁振子的存在，表面磁状态与体相不同，以及实验涉及磁性隧道结时势垒材料的性质。在这个项目中，一个创新的和探索性的方法来揭示Fe 3 O 4的自旋极化进行了研究。超薄无氧有机覆盖层将被施加到Fe 3 O 4的表面，以防止其氧化，并解除重建，最终目标是恢复其表面上的真正的自旋极化性质。理解到实现100%的自旋极化可能是困难的，本研究还旨在实现Fe 3 O 4中尽可能高的半金属性。同时制备高质量的外延膜和单晶Fe_3 O_4的解理面。一组有机覆盖层，显示承诺为指定的目的，包括苯乙烯，硫醇，石墨烯和碳？除尘？将沉积在表面上。化学和结构特性和自旋极化的表面与/无覆盖层将与国家的最先进的表征工具和磁性隧道结将进行额外的自旋极化测量。由于不可避免地存在不同于体相的表面态，因此探测Fe_3 O_4的真实自旋极化是一项极其困难的任务。该项目指出了一种新的和有前途的方法，通过在Fe 3 O 4的各种表面上施加覆盖层来克服这种障碍。这种保护表面免受氧化的努力，特别是提升重建的努力以前从未经过测试，就项目结果而言，风险很高。然而，潜在的影响将是巨大的，因为它导致了一个全新的和变革性的方法来揭示体自旋分辨的电子特性。非技术性：如果成功的话，实现Fe_3O_4的半金属化将是自旋电子材料研究的突破性进展，对自旋电子学科学技术产生巨大的影响。这个高风险高回报的项目对未来的信息技术有着直接的经济影响。研究生和本科生，特别是代表性不足的少数民族和女性，将获得与先进技术密切相关的凝聚态物理学和材料科学方面的培训机会。