Schizophrenic electrons in ruthenium-based oxides

Ruthenium and oxygen form many ternary compounds in which the Ru 4d states and O 2p states are strongly hybridized. In some such compounds, this hybridization leads to the loss of local magnetic moment character for the Ru, and in others it does not. The factors that determine which is the case are often subtle and poorly understood. The richness of structure types seen in ternary Ru oxides leads to a corresponding richness in electronic and magnetic properties. This article briefly describes the author's current views on these materials.