Neutron Scattering Studies of Magnetic Semiconductor Nanostructures

磁性半导体纳米结构的中子散射研究

• 批准号: 0138195
• 负责人: Jacek Furdyna
• 金额: $ 29.4万
• 依托单位: University of Notre Dame
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-15 至 2006-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0138195&HistoricalAwards=false
• 关键词: Neutron; Scattering; Studies; Magnetic; Semiconductor

This research is focused on an understanding of the magnetic structure and exchange interactions present in hybrid magnetic semiconductor materials. Semiconductor superlattices consisting of conventional II-VI materials in which alternate layers are antiferromagnetic and non-magnetic exhibit interlayer spin correlations of a surprisingly long range comparable to that in metallic systems. Neutron scattering is used as a probe of the magnetic structure, order parameter, and correlation range in these systems as a function of semiconductor doping. The results indicate that a magnetic interaction other than conventional superexchange is dominant. One of the present research objectives is to investigate in detail this exchange coupling and its dependence on electronic structure, strain effects, and types of doping. In addition to the II-VI materials, the research will focus on a detailed investigation of new ferromagnetic III-V systems, including the unusual dependence of the ferromagnetic transition temperature on composition and on the effect of thermal annealing. Neutrons will also provide direct information on the formation of ferromagnetic clusters or other nanoscale inhomogeneities that may affect the onset of infinite-range ferromagnetism. Finally, neutron reflectivity will be used to investigate the spatial dependence of the order parameter, and to investigate proximity effects between a hybrid III-V ferromagnetic semiconductor and an adjacent II-VI antiferromagnetic layer.Semiconductor and magnetic materials both play essential, but distinct, roles in many common electronic devices. Examples are computer memories made of semiconductors and hard disk drives utilizing magnetic materials. Recently the potential has arisen for a marriage of semiconducting and magnetic properties in a single material utilizing the concept of "spintronics." This research program is designed to use the powerful technique of neutron scattering to probe the magnetic state of materials that are both semiconducting and magnetic. The neutrons can be scattered by interacting with nuclei inside these systems, and in addition, since neutrons possess a magnetic moment, they can interact with magnetic fields inside materials. The result of such scattering provides direct information about the magnetic structure inside a material and over what distances the individual magnetic moments are coupled together. This type of information on the magnetism can be correlated with changes in the semiconducting properties of the materials as the system is "doped" with various chemical elements. The result provides necessary information to simultaneously optimize both the magnetic and the semiconducting aspects of these new compounds for future hybrid spintronic devices.

本研究的重点是了解混合磁性半导体材料中的磁性结构和交换相互作用。由传统的II-VI材料组成的半导体超晶格，其中交替层是反铁磁性和非磁性的，其层间自旋相关性的范围之长令人惊讶，可与金属系统相媲美。利用中子散射来探测这些体系的磁性结构、序参量和相关范围与半导体掺杂的关系。结果表明，除传统的超交换外，磁相互作用占主导地位。目前的研究目标之一是详细研究这种交换耦合及其对电子结构、应变效应和掺杂类型的依赖。除了II-VI材料外，研究还将重点研究新的铁磁III-V系统，包括铁磁转变温度对成分和热处理效果的不同寻常的依赖。中子也将提供铁磁团簇形成的直接信息或其他纳米尺度的不均匀性，这些不均匀性可能会影响无限范围铁磁的开始。最后，中子反射率将用于研究序参量的空间依赖性，并研究杂化III-V铁磁半导体与相邻的II-VI反铁磁层之间的邻近效应。半导体和磁性材料在许多常见的电子设备中都扮演着重要但不同的角色。例如由半导体制成的计算机存储器和利用磁性材料的硬盘驱动器。最近，利用“自旋电子学”的概念，在单一材料中结合半导体和磁性的潜力已经出现。本研究计划旨在利用强大的中子散射技术来探测半导体和磁性材料的磁性状态。中子可以通过与这些系统中的原子核相互作用而散射，此外，由于中子具有磁矩，它们可以与材料内部的磁场相互作用。这种散射的结果提供了关于材料内部磁性结构的直接信息，以及各个磁矩耦合在一起的距离。当系统被“掺杂”各种化学元素时，这种类型的磁性信息可以与材料的半导体特性的变化相关联。该结果为同时优化这些新化合物的磁性和半导体方面提供了必要的信息，以用于未来的混合自旋电子器件。