Structure Property Relationships in Transition Metal Oxides

这个项目涉及一类表现出挫败感的材料。这句话的意思与《牛津英语词典》的定义不太一样，《牛津英语词典》将动词“沮丧”定义为“阻碍”或“失望”，其衍生名词、形容词和副词都表达了同样的意思——失望。在我们的定义中，所涉及的是相互竞争的互动、约束或命令。想象一个有许多站点或节点通过电线或线程连接的网络。如果这些站点中有相当多的站点受到相互冲突的需求的影响，那么整个系统就会受到挫折。例如，在每个站点上都有一个指向特定方向的箭头。每一处的箭头方向信息由连接线传递。如果两个相邻的地点通过电线发出的指令相互竞争，也就是说，如果一个指令让箭头指向上方，另一个指令让箭头指向下方，那么我们在那个地点就会感到沮丧。挫折的概念渗透到现代科学的许多领域，可以在蛋白质折叠、位错传播甚至天体物理学等不同的主题中找到。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感表达。受挫的磁铁经常表现出奇怪的特性。例如，它们似乎经常违反热力学第三定律，即当温度接近绝对零度时，所有的空间无序都必须消失。在箭头的情况下，他们必须全部排成一行，形成一个有序的模式。挫折使这种困难在最好的情况下，真实的材料往往会发现意想不到的空间模式，这在普通材料中是观察不到的。我们的目标是确定磁性材料可能会受挫，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领域，而且还将阐明产生磁阻概念的几个相关领域。

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.