DEFECTS IN FRUSTRATED SYTEMS

受挫系统中的缺陷

• 批准号: EP/G004765/1
• 负责人: William Branford
• 金额: $ 123.64万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FG004765%2F1
• 关键词: DEFECTS; FRUSTRATED; SYTEMS; DEFECTS; FRUSTRATED; SYTEMS

In a complex system made up of many smaller units, each element will interact with all of its neighbours, and the system tries to arrange itself so that the most favourable bond is formed with each neighbour. However, sometimes the neighbours have requirements that are mutually incompatible and a compromise must be found. If this is the case we describe the system as being frustrated. Frustration occurs widely in nature and is thought to be critical to our understanding of such questions as how do our brains work? and how do proteins fold? The frustrated biological systems described are so complex and so important that the science of frustration has become a major research area and there is great demand for simpler model systems where the interaction strength can be tuned, the model system size can be varied, defects can be introduced in a controlled manner and individual elements can be manipulated, removed or their individual state recorded. In such an ideal system one could unite theory and experiment and begin to understand the underlying physics within this complexity. Magnetic frustration has proved to be the most successful area for finding model systems. Traditionally these were magnetic crystals prepared by solid-state chemistry. However it has recently been shown that it is possible to use nanotechnology to make arrays of magnetic bars sufficiently small and sufficiently close together that the magnetic interactions between them becomes very significant, and that novel geometries can be designed where the magnetic interactions cannot all be satisfied. This development opens up broad new avenues of research in model frustrated systems. In solid-state chemistry one is limited by nature in the geometrical arrangements that are possible, whereas with nanotechnology any pattern that will tessellate can be fabricated into an array, on any length-scale down to the minimum feature size of the lithography. Here I propose to study such ideal systems that are based on frustrated magnetic nanostructures. Our experience from frustrated magnetic chemical structures tells us that triangles and hexagons are the building blocks that favour magnetic frustration. The initial work was done on arrays of magnetic bars that were isolated from one another, but I plan to focus on electrically continuous lattices, such as the hexagonal honeycomb structure so that electrical current can pass through it. The electrical properties of magnetic materials are sensitive to the magnetic structure and so this gives a direct probe of the frustrated structure and one can study its dynamic response to changes in temperature and magnetic field. Magnetic force microscopy (MFM) and scanning Hall probe imaging will be used to image the magnetic structure during these experiments. These in-situ measurements will allow the change in electrical response to be correlated directly with the change in magnetic structure, and will provide important information of the nature of the coupling between the magnetic and electrical properties of ferromagnetic metals, and the role of topology, which is currently very important for new spin-based electronics or spintronics technology. In addition to improving knowledge of diverse other fields, the magnetic arrays that I will make are exciting in their own right. Their unusual and sensitive response to magnetic fields might be useful in sensors. Furthermore the strong coupling between all the elements, and the fact that the magnetic state of individual elements can be both written (changed by applying a magnetic field) and read, means they could potentially be used for novel types of computation, often described as neural networks because they work more like the brain than like a conventional computer.

在由许多较小单位组成的复杂系统中，每个元素都将与其所有邻居相互作用，并且该系统试图安排自身，以便与每个邻居形成最有利的纽带。但是，有时邻居的要求相互不相容，必须找到妥协。如果是这种情况，我们将系统描述为沮丧。挫败感在自然界中广泛发生，被认为对我们对大脑如何工作等问题的理解至关重要？蛋白质如何折叠？所描述的沮丧的生物系统是如此复​​杂，如此重要，以至于挫败科学已成为一个主要的研究领域，并且对更简单的模型系统的需求很大，可以调节相互作用强度，模型系统大小可以变化，可以以控制的方式引入缺陷，并且可以以控制的方式引入，并且可以操纵，删除，删除，删除，或他们的个人状态记录。在这样的理想系统中，人们可以团结理论和实验，并开始理解这种复杂性中的基本物理。事实证明，磁性挫败感是寻找模型系​​统的最成功领域。传统上，这些是通过固态化学制备的磁晶体。然而，最近已经证明，可以使用纳米技术使磁条的阵列足够小且足够接近，以使它们之间的磁相互作用变得非常重要，并且可以在无法满足磁性相互作用的情况下设计新的几何形状。这一发展开辟了模型沮丧系统中的广泛研究途径。在固态化学中，一个可能的几何排列受到了自然的限制，而纳米技术在纳米技术中，任何将镶嵌物的模式都可以在任何长度尺度上构成阵列，以至于光刻的最小特征大小。在这里，我建议研究基于沮丧的磁性纳米结构的理想系统。我们从沮丧的磁性化学结构中获得的经验告诉我们，三角形和六角形是有利于磁性挫败感的基础。最初的工作是在彼此分离的磁条阵列上进行的，但我计划专注于电连续的晶格，例如六边形蜂窝结构，以便电流可以通过它。磁性材料的电性能对磁性结构敏感，因此可以直接探测挫败的结构，并且可以研究其对温度和磁场变化的动态响应。磁力显微镜（MFM）和扫描霍尔探针成像将用于在这些实验过程中成像磁性结构。这些原位测量结果将使电响应的变化与磁性结构的变化直接相关，并将提供重要的信息，以提供铁磁金属的磁性和电气性质之间的耦合性质，以及拓扑的作用，目前对于新的基于自旋的基于基于自旋的电子产品或菠菜技术非常重要。除了提高对其他领域的知识外，我将制作的磁阵列本身令人兴奋。它们对磁场的异常和敏感反应可能在传感器中很有用。此外，所有元素之间的牢固耦合以及单个元素的磁态既可以写成（通过应用磁场进行更改）并读取的事实，这意味着它们可以可能用于新型计算类型的新型计算类型，通常被描述为神经网络，因为它们比大脑更像大脑，而不是像常规计算机一样。