Structure Property Relationships in Transition Metal Oxides

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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.