Perpendicular-Current Spin-Polarized Transport Studies

技术：本项目涉及两个相关的具有技术潜力的项目。金属磁性多层膜的垂直平面磁阻是下一代硬盘读头的竞争对手。比较精心挑选的新金属对之间界面的测量比电阻（样品面积乘以电阻），以及合作者进行的无自由参数计算，将使MSU小组测试对多层传输的基本理解，从而为技术设计提供基础。磁多层膜中自旋转移转矩诱导磁化开关和GHz辐射的产生对写入磁随机存取存储器和作为电流控制辐射源具有重要意义。为了弄清潜在的物理原理，密歇根州立大学的研究小组将测量开关电流和辐射如何随着磁性和非磁性金属的不同组合而变化。该小组还计划研究纳米柱和点接触（后者是一项合作）中漩涡的产生，包括反铁磁体的多层结构。这些项目将为研究生和本科生提供规划和开展前沿研究的经验。该项目涉及国际合作。非技术：该计划涉及两个项目，都涉及金属磁性多层，磁性和非磁性金属交替层，每层只有几个原子厚。电阻随外加磁场的变化，用垂直于多层材料层面的电流来测量，是下一代计算机硬盘读头的竞争对手。密歇根州立大学的研究小组将比较精心选择的金属对之间界面的特定电阻（样品面积乘以电阻）的测量结果，合作者将进行无自由参数计算。这种比较将为工艺设计提供依据。直到最近，磁性纳米柱中的磁性层（实际上是微小的磁体）的磁化只能在外部磁场的作用下反转（切换）。然而，有人预测并证明了一种新的现象，即自旋-传递-转矩（STT），通过让足够大的电流密度通过纳米柱，可以诱导这种开关。这种电流感应开关对于多层磁随机存取存储器的写入具有重要意义。STT还允许产生高频（千兆赫）电磁辐射，其技术上有趣的能力是通过改变施加的电流来改变频率。对不同磁性和非磁性金属组合的研究将阐明这两种现象背后的物理原理，从而有助于技术设计。这些项目为研究生和本科生提供了规划和开展前沿研究的经验。

Technical:This program involves two related projects with technological potential. Current-Perpendicular-to-Plane Magnetoresistance of metallic magnetic multilayers is a competitor for next generation read-heads for hard-disks. Comparing measured specific resistances (sample area times resistance) of interfaces between new pairs of carefully chosen metals, with no-free-parameter calculations made by collaborators, will let the MSU group test fundamental understanding of transport in multilayers, thus providing the basis for technological design. Spin-transfer-torque induced magnetization switching and generation of GHz radiation in magnetic multilayers is of interest for writing magnetic random access memory and as a current-controlled source of radiation. To clarify the underlying physics, the MSU group will measure how switching currents and radiation vary with different combinations of magnetic and non-magnetic metals. The group also plans to study generation of vortices in nanopillars and with point contacts (the latter a collaboration), including in multilayers with antiferromagnets. These projects will give graduate and undergraduate students experience in planning and carrying out cutting-edge research. The program involves international collaborations. Non-technical: This program involves two projects, both involving metallic magnetic multilayers, alternating layers of magnetic and non-magnetic metals, with each layer only a few atoms thick. The change in electrical resistance with applied magnetic field, measured with the current flowing perpendicular to the layer planes of the multilayer, is a competitor for next generation read-heads for computer hard-disks. The MSU group will compare measurements of specific resistances (sample area times resistance) of interfaces between carefully chosen pairs of metals, with no-free-parameter calculations by collaborators. This comparison will provide the basis for technological design. Until recently, the magnetizations of magnetic layers (effectively, tiny magnets) in magnetic nanopillars could be reversed (switched) only with an external magnetic field. However, it was predicted, and then shown, that a new phenomenon, spin-transfer-torque (STT), lets such switching be induced by passing a large enough current density through the nanopillar. Such current-induced switching is of interest for writing multilayer magnetic random access memory. STT also allows generation of high-frequency (giga-Hertz) electromagnetic radiation with the technologically interesting ability to change the frequency by varying the applied current. Studies of combinations of different magnetic and non-magnetic metals will clarify the physics underlying both phenomena, thereby assisting technological design. These projects give graduate and undergraduate students experience in planning and carrying out cutting-edge research.