Tunneling Studies of Ferromagnetic Junctions and Interfaces

铁磁结和界面的隧道研究

• 批准号: 9730908
• 负责人: Jagadeesh Moodera
• 金额: $ 33万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-09-01 至 2002-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9730908&HistoricalAwards=false
• 关键词: Tunneling; Studies; Ferromagnetic; Junctions; Interfaces

9730908 Moodera This experimental research project is concerned with electron tunnel junctions with electrodes of magnetic metals conceived in such a way that the tunneling current is controlled in a sensitive fashion by an applied magnetic field. Well characterized ferromagnetic tunnel junctions and interfaces will be prepared under clean and ultra high vacuum conditions to allow accurate and reproducible tunneling measurements, particularly on structures with 3d and 4f ferromagnetic metals. Spin polarization of the same films that make up the tunnel junction will also be measured by superconducting tunneling spectroscopy. The main thrust is to understand the physical mechanisms responsible for the observed magnetic field sensitivity. It is expected that this research will additionally lead to new results and techniques in condensed matter physics and new applications for magnetic technology.This research program is interdisciplinary in nature and has typically involved several undergraduate and high school students in its activities. These involvements are beneficial in the preparation of students for further study and for careers in industry, government laboratories or academia. %%% This experimental research project is concerned with a new class of electronic devices that the PI has discovered in his previously supported work, which are highly sensitive to magnetic field. The electrical resistance of the device, which is called a tunnel junction, changes when the device is placed in a magnetic field, and is said to exhibit magnetoresistance. This discovery has created interest worldwide because of the potential for improvements in technology. The main technological applications may be in magnetic sensors for computer hard drives, possibly for magnetic computer memory or logic elements, and for miscellaneous applications s uch as sensors to measure rotational speeds, eg, a tachometer. The basic tunnel junction is a capacitor-like device with a thin insulating oxide between two metal plates. In this case the oxide layer is so thin that electrons can transfer from one plate to the other by the quantum mechanical tunneling process. This process was firmly established and understood in detail in the late 1960's by basic physics researchers who realized that a tunnel junction device, if it could be fabricated with a sufficiently thin and homogeneous oxide layer, could be instrumental to understanding the nature of superconductivity. Ivar Giaever won the Nobel Prize in Physics in 1973 for his experiments on superconductivity which were based on his development of improved fabrication techniques and a more complete understanding of the physical behavior of tunnel junctions. The present PI has gone on from these earlier basic research results to find the magnetic effects which are very promising for applications in computers and other technologies. As in the earlier case, the PI here has perfected new and more careful experimental methods to clearly reveal the theoretically expected physical effects, in this case magnetic in nature. This project focuses on careful and systematic measurements on junction structures with metal electrodes of different ferromagnetic compositions, in order to better understand and maximize the sensitivity to magnetic field. This research program is interdisciplinary in nature and has typically involved several undergraduate and high school students in its activities. These involvements are beneficial in the preparation of students for further study and for careers in industry, government laboratories or academia. ***

9730908 Moodera这个实验研究项目与具有磁性金属电极的电子隧道连接有关，以使隧道电流通过施加的磁场以敏感的方式控制。 特征良好的铁磁隧道连接和界面将在干净且超高的真空条件下制备，以允许准确且可重现的隧道测量值，尤其是在具有3D和4F铁磁金属的结构上。构成隧道结的相同膜的自旋极化也将通过超导隧道光谱法测量。 主要的推力是了解负责观察到的磁场灵敏度的物理机制。可以预期，这项研究还将导致凝聚态物理和磁技术的新应用的新结果和技术。本研究计划本质上是跨学科的，通常涉及几名本科生和高中生的活动。这些参与对学生的准备以及行业，政府实验室或学术界的职业有益。 %% %%这个实验研究项目与PI在其先前支持的工作中发现的一类新的电子设备有关，这些设备对磁场高度敏感。该设备的电阻（称为隧道连接处）在设备放置在磁场中时会发生变化，据说具有磁性。由于有可能改善技术的潜力，因此这一发现引起了全世界的兴趣。主要的技术应用可以用于计算机硬盘驱动器的磁传感器，可能是用于磁性计算机记忆或逻辑元素的磁性传感器，以及用于测量旋转速度的传感器，例如，例如，转速计。基本隧道连接处是一种像电容器一样的设备，在两个金属板之间具有薄薄的绝缘氧化物。在这种情况下，氧化物层是如此薄，以至于电子可以通过量子机械隧穿过程从一个板转移到另一板。 基本物理学研究人员在1960年代后期牢固地建立和理解了这一过程，他们意识到，如果可以用足够薄且均匀的氧化物层制造隧道连接装置，则可能对理解超导性的性质有用。 伊瓦尔·吉弗（Ivar Giaever）于1973年获得了诺贝尔物理奖，因为他的超导性实验是基于他对改进的制造技术的发展以及对隧道交界的身体行为的更全面了解。 目前的PI已经从这些早期的基础研究结果中持续下去，以找到对计算机和其他技术应用非常有前途的磁效应。 与较早的情况一样，这里的PI完善了新的，更仔细的实验​​方法，以清楚地揭示理论上预期的物理效应，在这种情况下，在本质上是磁性的。 该项目着重于对具有不同铁磁组合物的金属电极的仔细和系统的测量，以便更好地理解和最大化对磁场的敏感性。该研究计划本质上是跨学科的，通常涉及几名本科生和高中生的活动。 这些参与对学生的准备以及行业，政府实验室或学术界的职业有益。 ***