SGER: Realization of Half-Metallicity in Magnetite

技术：虽然对许多人很有吸引力，但真正的半金属还没有在实验中观察到。对于所有理论预测的半金属，自旋极化的室温值远低于100%。实验报道的Fe3O4的室温自旋极化在20% ~ 80%之间。导致金属丰度缺乏的因素可能包括表面氧化和重构、磁振子的存在、表面磁态与体体不同以及实验中涉及磁性隧道结时势垒材料的性质。在这个项目中，我们将探索一种创新的、探索性的方法来揭示Fe3O4的自旋极化。超薄无氧有机覆盖层将被应用于Fe3O4表面，以防止其氧化并提升重建，最终目标是恢复其表面真正的自旋极化性质。了解到实现100%的自旋极化可能是困难的，本研究也旨在实现Fe3O4的最高半金属丰度。制备出高质量的Fe3O4单晶外延膜和劈裂表面。包括苯乙烯、硫醇、石墨烯和碳粉在内的一组有机涂层有望实现上述目的。会沉积在表面。将使用最先进的表征工具研究有/没有覆盖层的表面的化学和结构特性以及自旋极化，并将制作磁隧道结进行额外的自旋极化测量。由于不可避免地存在与本体不同的表面态，探测Fe3O4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颖而有前途的方法，通过在Fe3O4的各种表面上涂覆层来克服这种障碍。这种保护表面免受氧化的努力，特别是提升重建的努力，以前没有经过测试，就项目的结果而言，风险很高。然而，潜在的影响将是巨大的，因为它会导致一种全新的、变革性的方法来揭示体自旋分辨电子特性。非技术性：如果成功，实现Fe3O4的半金属丰度将是自旋电子材料研究的突破性成果，将对自旋电子学的科学技术产生巨大影响。这一高风险、高回报的项目将对未来的信息技术产生直接的经济影响。研究生和本科生，特别是少数族裔和女性，将获得与先进技术密切相关的凝聚态物理和材料科学方面的培训机会。

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.