Perpendicular-Current Spin-Polarized Transport Studies at Low Temperatures

科学技术正在推动人们试图理解金属磁性多层膜中自旋极化输运的物理原理。这种理解通常可以最直接地在几何结构中实现，即电流垂直于金属层（CPP），这是由密歇根州立大学的研究小组首创的。将进行新的实验来解决以下问题：(1)在某些非磁性/非磁性金属界面上发现的意外大自旋翻转的来源是什么？(2)单个磁畴壁和涡旋的阻力和动力学是什么？(3)界面粗糙度对Fe/Cr多层膜CPP磁阻的影响是什么？极化电流能穿透超导体多远？(5)是否可以观察到预测的交流约瑟夫森效应的磁模拟？这项研究将在教育学士、硕士和博士学生（包括女性和少数民族）方面发挥重要作用。这个项目的延伸部分包括监督密歇根科学奥林匹克竞赛的物理部分。在十年间，金属磁性多层中的巨磁电阻已经从发现变成了市场上的设备，比如用于高密度计算机磁盘驱动器的读磁头。但进一步的进展需要更大的磁阻和更小的探测器。下一代探测器的候选是巨磁阻多层探测器，用垂直于层的电流测量，这是密歇根州立大学的研究小组首创的一种几何结构。这种几何结构保证在较小的样品中具有较大的磁阻。但根本问题和实际问题仍有待解决。这个研究项目将以新颖的方式解决几个这样的问题，并将涉及学士、硕士和博士研究生，包括女性和少数民族。学生将学习如何提出重要的科学问题，组装最先进的设备来解决这些问题，并分析用设备获得的数据。

Science and technology are driving attempts to understand the physics underlying spin-polarized transport in metallic magnetic multilayers. Such understanding can usually be achieved most directly in the geometry with current flow perpendicular (CPP) to the metallic layers, pioneered by the Michigan State University group. Novel experiments will be performed to address the following questions: (1) What is the source of unexpectedly large spin-flipping found at certain non-magnetic/non-magnetic metal interfaces? (2) What are the resistances and dynamics of individual magnetic domain walls and vortices? (3) What is the importance of interfacial roughness on the CPP magnetoresistances of Fe/Cr multilayers? (4) How far can a polarized current penetrate into a superconductor? (5) Can a predicted magnetic analog of the AC Josephson effect be observed? This research will play an important role in educating BS, MS, and PhD students, including women and minorities. An outreach component of this program involves supervision of the physics portion of the Michigan Science Olympiad.In one decade, Giant Magnetoresistance in metallic magnetic multilayers has moved from discovery to marketed devices, such as read heads for high-density computer disk drives. But further progress requires still larger magnetoresistance and still smaller detectors. A candidate for the next generation of detectors is Giant Magnetorisistance multilayers measured with current flow perpendicular to the layers, a geometry pioneered by the group at Michigan State University. This geometry promises larger magnetoresistance in smaller samples. But both fundamental and practical issues still need to be resolved. This research program will address several such issues in novel ways, and will involve BS, MS, and PhD students, including women and minorities. The students will learn how to pose significant scientific questions, assemble state-of-the-art equipment to address them, and analyze data obtained with the equipment.