Structure Property Relationships in Transition Metal Oxides

过渡金属氧化物的结构性质关系

• 批准号: RGPIN-2016-05217
• 负责人: Greedan, John
• 金额: $ 2.19万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=683647
• 关键词: Structure; Property; Relationships; Transition; Metal

This project concerns a class of materials which exhibit frustration. What is meant is not quite the same as the Oxford English Dictionary definition where the verb, frustrate, is defined as to balk or disappoint and the derived nouns, adjectives and adverbs all convey the same idea disappointment. In our definition what is involved are competing interactions, constraints or commands. Imagine a network with many sites or nodes connected by wires or threads. If a significant number of these sites are subject to conflicting demands, then the entire system is said to be frustrated. For example, take the case where at each site there exists an arrow pointing in a specific direction. Information about the direction of the arrow at each site is conveyed by the connecting wires. If the commands from two adjacent sites through the wires are in competition, i.e., if one command is for the arrow to point up and the other for the arrow to point down, then we have frustration at that site. The concept of frustration permeates many areas of modern science, being found in such disparate topics as protein folding, dislocation propagation and even astrophysics. Magnetic materials based on equilateral triangular networks or lattices provide the cleanest expression of frustration. Frustrated magnets often exhibit bizarre properties. For example they often seem to violate the Third Law of Thermodynamics which states that as the temperature approaches absolute zero, all spatial disorder must disappear. In the case of the arrows, they must all line up to form a well ordered pattern. Frustration renders this difficult at best and real materials will often find unexpected spatial patterns which are not observed in ordinary materials. Our goal is to identify magnetic materials which are likely to be frustrated, cool them down to low temperatures and attempt to unravel the patterns displayed. The discoveries made will illuminate not only the field of magnetic frustration but also the several related areas in which the concept of frustration arises.**

该项目涉及一类表现出挫折感的材料。它的意思与《牛津英语词典》的定义不太一样，在《牛津英语词典》中，动词frustrate被定义为犹豫或失望，派生的名词、形容词和副词都表达了同样的意思失望。在我们的定义中，所涉及的是竞争性的相互作用、约束或命令。想象一个网络，有许多站点或节点通过电线或线程连接。 如果这些网站中有相当多的网站受到相互冲突的要求，那么整个系统被称为受挫。例如，在每个站点都有一个指向特定方向的箭头。每个部位的箭头方向信息由连接线传达。如果通过线路来自两个相邻站点的命令处于竞争中，即，如果一个命令是让箭头指向上，而另一个命令是让箭头指向下，那么我们在该站点会遇到挫折。挫折的概念渗透到现代科学的许多领域，在蛋白质折叠，位错传播甚至天体物理学等不同的主题中都可以找到。基于等边三角形网络或晶格的磁性材料提供了最清晰的挫折表达。受挫折的磁铁往往表现出奇怪的性质。例如，它们似乎经常违反热力学第三定律，该定律指出，当温度接近绝对零度时，所有空间无序必须消失。在箭头的情况下，它们必须全部排成一行以形成有序的图案。挫折使这一困难充其量和真实的材料往往会发现意想不到的空间模式，这是没有观察到的普通材料。我们的目标是识别可能会受到挫折的磁性材料，将它们冷却到低温，并试图解开显示的模式。这些发现不仅将阐明磁阻挫领域，而且将阐明阻挫概念产生的几个相关领域。