Magnetic Phenomena on the Nanometer Scale

纳米尺度的磁现象

• 批准号: 0101814
• 负责人: Chia-Ling Chien
• 金额: $ 36万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-08-01 至 2004-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0101814&HistoricalAwards=false
• 关键词: Magnetic; Phenomena; Nanometer; Scale

This research is focused on the investigation of the spin polarization of ferromagnetic metals and the switching of ferromagnetic components. These phenomena, occurring on the nanometer scale, are of crucial importance to magnetoelectronic devices. We propose to use the point-contact Andreev reflection technique, with appropriate analyses, to measure the intrinsic spin polarization of a variety of materials, especially CrO2 and the Heusler alloys, which have been predicted to be 100% spin polarized. We also propose to address key issues in multilayers with exchange bias, particularly the type of antiferromagnetic spin structure present, antiferromagnetic domains, and the switching of exchange-coupled systems using synthetic antiferromagnets. The graduate students involved in the project receive training in cutting-edge technology of careers in academe, industry and government.Magnetoelectronic devices are new devices that manipulate both spin (magnetic dipole moment) and charge of electrons as opposed to only charge of electrons in traditional electronic devises. These new devices depend crucially on the substantial spin polarization of certain ferromagnetic materials (a difference in the number of resident spin-up and spin-down electrons) through which the itinerant electrons flow, and the ability to switch the magnetization of the ferromagnet channels. Example of such devices employing these components include giant magnetoresistance (GMR) read-heads in virtually all computers manufactured today, and magnetic random access memories (MRAM) that one day may be replace the current dynamic random access memory (DRAM) used in current computers. This work is directed at measuring the intrinsic spin polarization of metals (the ferromagnetic channels) using the technique of Andreev reflection, which depends on fundamental properties of superconducting junctions that are employed in the experiments. The other part of this work is to understand how thin magnetic layers, which exist in many magnetoelectronic devices, can be made to switch easily by a small external field, or be designed to resist switching. Students in this program will receive extensive training in physics, new materials, and measuring techniques to enable them to pursue careers in academe, as well as in industrial and government labs.

本论文主要研究铁磁金属的自旋极化和铁磁组分的翻转。 这些现象发生在纳米尺度上，对磁电子器件至关重要。 我们建议使用的点接触Andreev反射技术，适当的分析，以测量各种材料，特别是CrO2和Heusler合金，已被预测为100%的自旋极化的固有自旋极化。 我们还建议解决交换偏置多层膜中的关键问题，特别是反铁磁自旋结构的类型，反铁磁畴，以及使用合成反铁磁体的交换耦合系统的切换。 参与该项目的研究生将接受尖端技术的培训，这些技术将在工业、工业和政府部门中发挥作用。磁电器件是一种新型器件，它可以操纵电子的自旋（磁偶极矩）和电荷，而不是传统电子器件中的电子电荷。 这些新器件关键取决于某些铁磁材料的实质性自旋极化（驻留自旋向上和自旋向下电子的数量差异），巡游电子流过这些铁磁材料，以及切换铁磁通道磁化的能力。 采用这些组件的这种设备的示例包括当今制造的几乎所有计算机中的巨磁阻（GMR）读取头，以及有朝一日可能取代当前计算机中使用的当前动态随机存取存储器（DRAM）的磁性随机存取存储器（MRAM）。 这项工作是针对测量的固有自旋极化的金属（铁磁通道）使用安德烈耶夫反射的技术，这取决于在实验中采用的超导结的基本属性。 这项工作的另一部分是了解如何薄的磁性层，存在于许多磁电子器件，可以很容易地切换由一个小的外部磁场，或被设计为抵制切换。 该计划的学生将接受物理，新材料和测量技术方面的广泛培训，使他们能够在工业和政府实验室中从事职业生涯。