Block Copolymer Self-Assembly-Directed Mesoporous Gyroidal Strontium Titanate with Room-Temperature Ferromagnetism.

Abstract

Block copolymer structure direction has been demonstrated as a technique to impart nanostructure and mesoporosity with enhanced properties to a variety of metal oxides for applications including catalysis, energy conversion and storage, as well as superconductivity. Such approaches require polymer-compatible solution synthesis routes toward oxide nanoclusters, which are not generally available for a broad range of functional materials. Here, we report an acetic acid-based sol-gel-derived method for the synthesis of mesoporous ternary strontium titanate with a morphology consistent with alternating gyroid. In-depth structural characterization suggests a periodic gyroidal structure and phase purity of the resultant perovskite. Magnetometry reveals that these normally diamagnetic oxide materials are ferromagnetic at room temperature. This magnetism is significantly enhanced by mild vacuum annealing, suggesting oxygen vacancies as the source of ferromagnetism. Block copolymer self-assembly-directed mesoporous ternary perovskites may provide a rich platform for studying surface and interfacial effects in surface-dominated systems by enhancing normally dilute surface phenomena.