Self-organized two-dimensional onions

Spontaneously self-assembled onion-type nanostructures based on block copolymers as templating materials are reported. Polystyrene-poly(ethylene oxide) diblock copolymer containing CoFe2O4 and Pb1.1(Zr0.53Ti0.47)O3 precursors segregated to the two microdomains forms well-ordered templated lamellar structures. Onion-type nanostructures have been induced by room temperature solvent annealing for 64 h in a magnetic field of 0.8 T oriented perpendicularly to the plane of film. The recorded images suggest that the Lorentz force acting on charges in the paraelectric precursor induces a circular component of the diffusion flux that leads to the onion formation. This templating process opens a route for nanometer-scale patterning of magnetic toroids.