Noise Investigations of Condensed Matter Systems

凝聚态系统的噪声研究

• 批准号: 9305763
• 负责人: Michael Weissman
• 金额: $ 30万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-07-01 至 1996-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9305763&HistoricalAwards=false
• 关键词: Noise; Investigations; Condensed; Matter; Systems

Most materials exhibit slow fluctuations, with a broad distribution of characteristic rates, in a variety of electrical, mechanical, magnetic, and optical parameters. Despite the ubiquity of a simple form (1/f) for the frequency spectrum of such fluctuations, a wide variety of mechanisms are involved, as has been demonstrated in past experiments in this project. These fluctuations are of interest for two general reasons: First, they limit the performance of a variety of sensors and devices. Second, they provide a useful tool to study fundamental properties of materials, especially glasses, which exhibit partially frozen random structures. This proposal applied fluctuation techniques to investigate several materials with some of the most common forms of frozen disorder. These include amorphous silicon, charge-density wave systems, several types of spin-glasses, spin-density wave magnetic domains, domain fluctuations in ferromagnets, and the new giant-magneto-resistive materials. The work will emphasize particularly the interplay between the chaotic behavior of some driven systems and the frozen randomness present in equilibrium. %%% New technologies often require new materials and increasingly involve the use of very small structures. In small structures such properties as the electrical resistivity of materials are generally not constant, but fluctuate in time. Such fluctuations are often the most important factor in limiting the miniaturization of devices. Past experiments in this project have shown that a wide variety of mechanisms lie behind these fluctuations in different materials. This proposal explores the origins of the fluctuations in some technically important materials, including amorphous silicon and the new giant-magneto-resistive materials. Particular attention is paid to developing a general understanding of the very common but poorly understood types of materials known as glasses, which exhibit partially frozen random structures.

大多数物质呈现出缓慢的波动，具有广泛的分布 的特征率，在各种电气，机械， 磁性和光学参数。 尽管简单的 形式（1/f）对于这种波动的频谱， 涉及多种机制，如 在这个项目中的实验。 这些波动是 有两个原因：第一，他们限制了 各种传感器和设备的性能。 二是 为研究材料的基本性质提供了一个有用的工具， 尤其是玻璃，其表现出部分冻结的随机 结构. 该提案采用波动技术， 研究了几种材料，其中一些最常见的形式， 冰冻紊乱症 其中包括非晶硅、电荷密度 波系统，几种自旋玻璃，自旋密度波 磁畴，铁磁体中的磁畴波动，以及新的 巨磁阻材料 工作将强调 特别是一些人的混乱行为 驱动系统和冻结随机性存在于平衡中。 %%% 新技术通常需要新材料， 使用非常小的结构。 在这样的小结构中， 材料的电阻率等特性通常 不是恒定的，而是随时间波动的。 这种波动往往 限制小型化的最重要因素 装置. 该项目过去的实验表明， 在不同的环境中，这些波动背后有各种各样的机制。 材料. 这一建议探讨了波动的起源 在一些技术上重要的材料中，包括非晶 硅和新的巨磁阻材料。 特别 注意发展一个非常普遍的理解， 常见但知之甚少的材料类型称为玻璃， 其表现出部分冻结的随机结构。