RUI: Dynamic Properties of Magnetic Multilayers and Nanostructures

RUI：磁性多层和纳米结构的动态特性

• 批准号: 0303563
• 负责人: Zbigniew Celinski
• 金额: --
• 依托单位: University of Colorado at Colorado Springs
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-06-01 至 2006-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0303563&HistoricalAwards=false
• 关键词: RUI; Dynamic; Properties; Magnetic; Multilayers

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.

该凝聚态物理项目重点研究磁性多层和纳米结构的特性。 虽然交换耦合和巨磁阻等静态行为受到了大部分关注，但理解这些材料的动态行为也存在重要问题。 在这一领域提出了三项研究。 (1)交换耦合磁性多层膜的动态行为。 这将通过铁磁共振方法在低场进行研究。 与磁性多层中的磁共振情况不同，该区域被称为反共振条件（趋肤深度变大并且材料“打开”）尚未得到研究。 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，我们打算研究一些磁性多层膜中发生的非常强的低场吸收。 (2)层状结构中交换耦合强度方差的研究。 现在已经针对许多材料组合测量了通过非磁性间隔材料确定两个铁磁体之间的交换耦合强度。 相比之下，这种交换耦合强度的变化尚未得到解决，尽管它在结构的动态特性中起着至关重要的作用。 将通过使用铁磁共振测量的线宽信息来测量方差。 这将针对金属多层和铁磁体/反铁磁体结构进行，其中界面粗糙度可能会在交换耦合中产生很大的变化。 (3)超小图案结构的动力响应。 这将包括对超小（直径 10 nm）磁点阵列以及单一材料点（铁和坡莫合金）和多层（铁/钯和钴/钯）点的动态测量。 Co/Pd 点特别有趣，因为可以通过改变层的厚度将磁化强度从面内改变为面外。 该项目还将研究点阵列的磁性质量如何取决于制造工艺（离子束蚀刻和通过蛋白质掩模沉积）、点分离和点结构。 这些测量对于磁存储技术非常重要。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接受基础实验技术和尖端技术的培训。这项培训将为他们在学术界、工业界或政府部门的一系列职业做好准备。层状磁性材料领域在过去十年中异常活跃。 诸如巨磁阻之类的重要发现已经在计算机存储器中得到应用，从而导致磁硬盘系统的显着改进。 该项目将包括对这些新型层状材料的研究，以探索基础物理和可能的应用。 第一项研究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，材料会抑制电磁波。 尽管该功能对于高频信号处理具有重要的技术前景，但尚未经过实验测试。 将制造并测试磁性多层膜，看看其是否按预期工作以及在技术上是否可用。 第二个主要主题涉及这些层状材料中的磁耦合。 特别令人感兴趣的是这种耦合如何沿层的不同位置变化。 这很重要，因为这种变化在上述高频响应中起着重要作用。 最终项目涉及超小磁点。 这些超小点的直径只有约 50 个原子，因此它们的特性与我们日常处理的材料截然不同。 实验将研究改变点的形状以及分层图案如何改变这些点的磁化方向。 这对于磁记录来说非常重要，因为这些微小点的阵列可以存储大量信息。 首席研究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，拟议的活动将继续强调对教育和人力资源开发的承诺。 该项目的学生接受严格的物理和材料培训，可以从事学术或工业科学职业。