Neutron and Synchrotron Radiation Scattering Studies of New Ferromagnetic Semiconductors and their Nanostructures

新型铁磁半导体及其纳米结构的中子和同步辐射散射研究

• 批准号: 0204105
• 负责人: Tomasz Giebultowicz
• 金额: $ 29.63万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-08-01 至 2006-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0204105&HistoricalAwards=false
• 关键词: Neutron; Synchrotron; Radiation; Scattering; Studies

Magnetic semiconductors currently receive a great deal of attention because these materials are expected to revolutionize the computer and communication technologies. The new-generation electronics, usually referred to as "spintronics", exploits not only the electronic charge, but also its spin - a feature not taken advantage of in the presently used semiconductor chips. A number of teams in the US, Japan and Europe are now competing to find the best ways of synthesizing new magnetic semiconductors suitable for building practical spintronics devices.Parallel to the ongoing efforts of material technologists, much effort is also needed from condensed matter physicists to characterize the magnetism and other related properties of the new emerging materials The scattering of neutrons and synchrotron radiation are two powerful experimental tools that allow one to obtain a detailed atomic-level insight into the magnetism of a condensed matter system. The aim of this project is to use these two techniques for investigating new spintronics materials, with particular emphasis on the physical mechanism underlying their magnetism. It should be stressed that the mechanism giving rise to semiconductor magnetism is not exactly the same as in most other known magnetic systems (e.g., iron), and not all details of that mechanism have yet been fully understood. The building blocks of future spintronics devices will be nanostructures such as superlattices - i.e., "sandwiches" made of alternating extremely thin layers of magnetic and non-magnetic semiconductors. One question concerning such sandwiches - very important from the viewpoint of designing spintronics devices - is how two magnetic layers "communicate" across the intervening non-magnetic "spacer". Neutron and synchrotron radiation tools are particularly well suited for investigating these phenomena. Such studies are also an essential part of our project.Ferromagnetic semiconductors (FMSC) currently receive a great deal of attention because such materials are essential for developing "spintronics" - a new-generation electronics in which not only the current magnitude, but also its spin polarization can be controlled. The aim of this project is to exploit the potential of neutron and synchrotron radiation scattering techniques to shed light on several important issues concerning newly synthesized FMSC materials and their nanostructures. It should be stressed that FMSCs differ in many respects from "conventional" ferromagnetic materials, which are either metals or insulators. As in metals, the magnetism of certain novel FMSC systems (e.g., Ga(Mn)As) is induced by carriers - however, not by electrons, but by holes. Details of this new physical mechanism have yet to be understood. Inelastic neutron scattering tools may greatly help in such studies because they enable one to obtain very accurate values of the exchange parameters characterizing the interactions between magnetic ions. Another important issue is understanding the mechanism of exchange interaction transfer between FMSC layers separated by a non-magnetic spacer. Neutron and synchrotron radiation reflectometry are powerful tools for investigating such interactions. These techniques also enable one to study structural defects in the interface regions in heterostructures made of magnetic/nonmagnetic semiconductors. Such defects may significantly influence the performance of future spintronics devices. Therefore, insight into this issue is of considerable importance.

磁性半导体目前受到了极大的关注，因为这些材料有望彻底改变计算机和通信技术。新一代的电子学，通常被称为“自旋电子学”，不仅利用了电子电荷，而且利用了它的自旋--这是目前使用的半导体芯片中没有利用的一个特征。美国、日本和欧洲的一些团队现在正在竞相寻找合成新的磁性半导体的最佳方法，这些磁性半导体适用于建造实用的自旋电子器件。与材料技术专家正在进行的努力平行，凝聚态物理学家还需要付出很大的努力来描述新出现的材料的磁性和其他相关性质。实验工具，使人们能够获得一个详细的原子水平的洞察到凝聚态物质系统的磁性。该项目的目的是使用这两种技术来研究新的自旋电子学材料，特别强调其磁性的物理机制。应该强调的是，产生半导体磁性的机制与大多数其他已知的磁性系统（例如，铁），并且尚未完全理解该机制的所有细节。未来自旋电子器件的构建块将是纳米结构，如超晶格-即， 由磁性和非磁性半导体交替极薄的层制成的“三明治”。 从设计自旋电子器件的角度来看，这种三明治结构的一个重要问题是，两个磁性层如何通过中间的非磁性“间隔物”进行“通信”。中子和同步辐射工具特别适合研究这些现象。铁磁半导体（FMSC）是发展“自旋电子学”（spintronics）的重要材料，是不仅可以控制电流大小，还可以控制自旋极化的新一代电子学。该项目的目的是利用中子和同步辐射散射技术的潜力，阐明有关新合成的FMSC材料及其纳米结构的几个重要问题。应该强调的是，FMSC在许多方面不同于“常规”铁磁材料，后者是金属或绝缘体。与金属一样，某些新型FMSC系统的磁性（例如，Ga（Mn）As）是由载流子诱导的-然而，不是由电子，而是由空穴诱导的。这种新的物理机制的细节还有待了解。非弹性中子散射工具可能会大大有助于在这样的研究，因为它们使人们能够获得非常准确的值的交换参数表征磁性离子之间的相互作用。另一个重要的问题是理解由非磁性间隔物分隔的FMSC层之间的交换相互作用转移的机制。中子和同步辐射反射仪是研究这种相互作用的有力工具。 这些技术也使人们能够研究在磁性/磁性半导体异质结构的界面区域的结构缺陷。这种缺陷可能会显著影响未来自旋电子器件的性能。因此，深入了解这一问题是相当重要的。