RUI: Dynamic Properties of Magnetic Multilayers and Nanostructures

这个凝聚态物理学项目的重点是磁性多层膜和纳米结构的特性。 虽然静态行为，如交换耦合和巨磁电阻已经得到了最大的关注，有重要的问题，在理解这些材料的动力学行为以及。 在这方面提出了三项研究。 (1)交换耦合磁性多层膜的动力学行为。 这将通过铁磁共振方法在低磁场下进行研究。 与磁多层膜中磁共振的充分研究情况不同，该区域被称为反共振条件-其中趋肤深度变大并且材料“打开”-尚未被研究。 这是令人惊讶的，因为理论计算表明多层膜中的反共振与单层膜中的反共振非常不同，并且因为这种效应有重要的技术应用。 此外，我们打算调查一个非常强的低场吸收，发生在一些磁性多层膜。 (2)层状结构中交换耦合强度变化的研究。 目前已对多种材料组合测定了两个铁磁体通过隔离层材料的交换耦合强度。 与此相反，这种交换耦合强度的变化还没有得到解决，即使它在结构的动态特性中起着至关重要的作用。 将通过使用来自铁磁共振测量的线宽信息来测量方差。 这将是这样的金属多层膜和铁磁/反铁磁结构，界面粗糙度可能会产生很大的变化，在交换耦合。 (3)超小型图案化结构的动态响应。 这将包括对超小（10 nm直径）磁点阵列的动态测量，以及单材料点（Fe和坡莫合金）和多层（Fe/Pd和Co/Pd）点。 Co/Pd点是特别有趣的，因为磁化可以通过改变层的厚度从面内改变到面外。 该项目还将研究点阵列的磁性质量如何取决于制造过程（通过蛋白质掩模的离子束蚀刻和沉积），点分离和点结构。 这些测量对于磁记忆技术将是重要的。PI都有将教育与研究相结合以及促进多样性的历史，并且在拟议的活动中将继续强调这种对教育和人力资源开发的承诺。 参与该项目的研究生和本科生将接受尖端技术的基本实验技术培训。这种培训将为他们在工业，工业或政府部门的一系列职业生涯做好准备。在过去的十年中，层状磁性材料领域一直非常活跃。 诸如巨磁电阻等重要发现已经在计算机存储器中实现，从而导致磁硬盘系统的重大改进。 该项目将包括对这些新的分层材料的研究，以探索基础物理和可能的应用。 这些调查的第一个涉及这些材料在高频下的电磁响应。 理论计算表明，在特定频率下，这种材料会排斥电磁波。 这个特性还没有经过实验测试，即使它有显着的高频信号处理的技术承诺。 磁性多层膜将被制造和测试，看看它是否像预测的那样工作，以及它是否在技术上可用。 第二个主要议题是这些层状材料中的磁耦合。 特别感兴趣的是这种耦合如何沿着层沿着从位置到位置变化。 这一点很重要，因为这种变化在上述高频响应中起着重要作用。 最后一个项目涉及超小磁点。 这些超小点的直径只有大约50个原子，因此它们的性质与我们日常处理的材料非常不同。 实验将研究如何改变点的形状以及分层模式可以改变这些点的磁化方向。 这对磁记录来说非常重要，因为这些微小的点阵列可以存储大量的信息。 主要研究人员在将教育与研究相结合以及促进多样性方面有着悠久的历史，在拟议的活动中将继续强调对教育和人力资源开发的承诺。 该计划的学生接受严格的物理和材料培训，并可以从事学术或工业科学的职业。

This condensed matter physics project focuses on the properties of magnetic multilayers and nanostructures. While static behaviors, such as exchange coupling and giant magnetoresistance have received most of the attention, there are important issues in understanding the dynamical behavior of these materials as well. In this area three studies are proposed. (1) Dynamic behavior of exchange-coupled magnetic multilayers. This will be studied at low fields via ferromagnetic resonance methods. This area, unlike the well studied case of magnetic resonance in magnetic multilayers, is known as the anti-resonance condition - where the skin depth becomes large and the material "opens up" - has not been investigated. This is surprising since theoretical calculations indicate that anti-resonance in multilayers is very different from anti-resonance in single films and because there are significant technological applications for this effect. In addition we intend to investigate a very strong low-field absorption that occurs in some magnetic multilayers. (2) Studies of the variance of exchange coupling strength in layered structures. The determination of th e exchange coupling strength between two ferromagnets through a nonmagnetic spacer material has now been measured for many material combinations. In contrast, the variance in this exchange coupling strength has not been addressed, even though it plays a critical role in the dynamic properties of the structure. The variance will be measures by using linewidth information from ferromagnetic resonance measurements. This will be done for the metallic multilayers and for ferromagnet/antiferromagnet structures where interface roughness is likely to create large variations in exchange coupling. (3) Dynamic response of ultra-small patterned structures. This will include dynamic measurements on ultra-small (10 nm diameter) magnetic dot arrays, and both single material dots (Fe and Permalloy) and multilayer (Fe/Pd and Co/Pd) dots. The Co/Pd dots are particularly interesting in that the magnetization can be changed from in-plane to out-of-plane by changing the thicknesses of the layers. The project will also investigate how the magnetic quality of the dot arrays depends on fabrication process (ion-beam etching and deposition through a protein mask), dot separation, and dot structures. These measurements will be important for magnetic memory technologyThe PI's all have a demonstrated history of integrating education with research as well as promoting diversity, and this commitment to education and human resource development will continue to be emphasized in the proposed activity. Graduate and undergraduate students involved in the project receive training in fundamental experimental techniques with cutting edge technology. This training will prepare them for a range of careers in academe, industry or government.The field of layered magnetic materials has been exceptionally active in the last decade. Important discoveries such as giant magnetoresistance have already been implemented in computer memories, leading to significant improvements in magnetic hard disk systems. The project will include studies of these new layered materials to explore fundamental physics and possible applications. The first of these investigations deals with the electromagnetic response of these materials at high frequencies. Theoretical calculations show that at particular frequencies the material rejects electromagnetic waves. This feature has not been tested experimentally even though it has significant technological promise for high frequency signal processing. Magnetic multilayers will be fabricated and tested to see if this works as predicted and if it is usable technologically. The second main topic deals with the magnetic coupling in these layered materials. Of particular interest is how this coupling varies from position to position along the layers. This is important because this variation plays an important role in the high frequency response described above. The final project deals with ultra-small magnetic dots. These ultra-small dots are only about 50 atoms in diameter so they can have very different properties than materials we deal with on an everyday basis. The experiments will study how varying the shape of the dots as well as the layering pattern can change the magnetization direction in these dots. This could be very important for magnetic recording because an array of these tiny dots could store an enormous amount of information. The Principal Investigators have a demonstrated history of integrating education with research as well as promoting diversity, and this commitment to education and human resource development will continue to be emphasized in the proposed activity. Students in this program receive rigorous training in physics and materials, and can pursue careers in either academic or industrial science.