CAREER: Spin Polarization Spectroscopy of Complex Magnetic Materials and Spin Electronic Devices

利用电子设备中电子(或空穴)自旋的可能性导致了自旋电子学这一新领域的出现。自旋电子器件的效率强烈地依赖于铁磁体中的自旋极化程度。特别是，100%自旋极化的半金属对下一代电子设备具有至关重要的作用。从实验上证实这种高度自旋极化的材料体系的存在对自旋电子学至关重要。这项研究的重点是加深对高度自旋极化材料中自旋输运的基础知识的理解，以及对新的高度自旋极化材料的研究。我们提出了一个内聚性的研究计划，以进一步发展和扩展点接触安德列夫反射(PCAR)光谱，并将其应用于稀磁半导体和金属合金的自旋极化测量。此外，我们还建议探索一种新的基于安德列夫反射的非挥发性铁磁超导器件的可行性。该方案还包括对具有潜在原位能力的空间分辨自旋极化测量(自旋映射)的初步研究。PI最近首次在非磁性半导体的点接触几何中观察到安德列夫反射，并在磁性半导体中获得了一些初步结果。这些结果有力地表明，PCAR技术可以成为一种可行的稀磁半导体测量技术，这对该领域的未来发展至关重要。除了自旋极化测量外，还将进行输运、磁性、化学和结构分析，以详细研究以下材料系统：1)稀磁和非磁性半导体：非磁性半导体(如BeGaAs)。磁性半导体：GaMnSb、GaMnAs、InMnSb和MnAs。2)其他理论预测的半金属：双钙钛矿(Sr2FeMoO6)和CoxFe1-xS2。作为其研究计划的更广泛影响的一部分，PI正计划促进与当地行业(特别是德尔福汽车公司)和HYPRES(铁磁/超导非挥发性器件)的合作。他还与橡树岭国家实验室合作，在那里，PI是新的纳米材料科学中心的“大学冠军”之一。空间分辨自旋极化测量(自旋映射)，并将与该中心合作进行调查。PI积极参与一项扩大少数群体参与物理学的综合方案。他给高中生做公开演讲，解释成为一名物理学家需要做些什么，并试图消除一种心理障碍，这种心理障碍往往会阻止许多少数族裔学生和女性成为科学家。他正在为底特律科学中心提供与物理相关的展品的内容和科学质量方面的建议。PI的两个主要教育目标，与他的研究相结合，是：1)开发一项试点计划，旨在将WSU的高级研究项目作为课程的必修部分；2)开发一门新的研究生水平课程“磁性、磁性设备和纳米技术”。本课程将介绍磁性、GMR和TMR器件和传感器、新型磁性材料、自旋输运和自旋极化测量以及现代纳米制造技术的基本概念。

The possibility of exploiting the spin of electrons (or holes) in electronic devices has led to the emergence of the new field of spintronics. The efficiency of spintronics devices is strongly dependent on the degree of the spin polarization in a ferromagnet. In particular, half-metals, which are 100% spin-polarized, are of fundamental importance for the next-generation of electronic devices. The experimental confirmation of the existence of such highly spin-polarized materials systems is vital to spintronics. The proposed research focuses on developing a fundamental understanding of the basics of spin transport in highly spin-polarized materials and on the ongoing search for novel highly spin-polarized materials.We propose a cohesive research program to further develop and expand Point Contact Andreev Reflection (PCAR) Spectroscopy and to apply it to the spin polarization measurements in dilute magnetic semiconductors and metal alloys. In addition, we propose to explore the viability of a new nonvolatile ferromagnet-superconductor device based on Andreev reflection. The proposal also includes an initial exploratory study of spatially resolved spin polarization measurements (Spin Mapping) with potential in situ capabilities.The PI has recently observed for the first time Andreev reflection in the point contact geometry in a non-magnetic semiconductor, and has obtained some preliminary results in magnetic semiconductors. These results strongly indicate that the PCAR technique can become a viable measurement technique for dilute magnetic semiconductors, which is crucial for the future development of this field. In addition to the spin polarization measurements, transport, magnetic, chemical, and structural analysis will be performed to study in detail the following materials systems: 1) Dilute magnetic and non-magnetic semiconductors: Non-magnetic semiconductors (e.g., BeGaAs). Magnetic semiconductors: GaMnSb, GaMnAs, InMnSb, and MnAs.2)Other theoretically predicted half-metals: double perovskites (Sr2FeMoO6,) and CoxFe1-xS2.As part of the broader impact of his research proposal the PI is planning to promote collaboration with the local industry (especially Delphi Automotive) and with HYPRES (on ferromagnet/superconductor nonvolatile device). He is also collaborating with Oak Ridge National Laboratory, where the PI is one of the "University Champions" of the new Nanophase Materials Science Center. The spatially resolved spin polarization measurements (Spin Mapping) and will be investigated in partnership with the Center.The PI is actively involved in a comprehensive program to broaden participation of minorities in physics. He gives public lectures to high school students to explain what is involved in being a physicist and to try to eliminate a psychological barrier that often prevents many minority students and women from becoming a scientist. He is advising the Detroit Science Center on the content and scientific quality of their physics-related exhibits. The PI's two major educational goals, integrated with his research, are:1)Develop a pilot program aimed at introducing a Senior Research Project at WSU as a required part of the curriculum.2)Develop a new graduate level course "Magnetism, Magnetic Devices and Nanotechnology". This course will introduce the basic concepts in magnetism, GMR and TMR devices and sensors, novel magnetic materials, spin transport and spin polarization measurements, and modern nanofabrication techniques.