Hierarchical assembly of magnetic L10-ordered FePt nanoparticles in block copolymer thin films

Abstract

The self-assembly process and local magnetic properties of asymmetric poly(styrene-block-ethylene oxide) (PS-b-PEO) copolymer thin films blended with L1₀-ordered FePt nanoparticles are studied. During the solvent annealing process, it is shown that L1₀-ordered FePt nanoparticles covered with short dopamine-terminated-methoxy poly(ethylene oxide) (mPEO-Dopa) are localized within spherical PEO domains having an inter-domain spacing of about 43.2 nm. The magnetic properties of the nanocomposite thin films were then investigated using magnetic force microscopy (MFM). MFM results reveal that each spot (magnetic signal), resulting from the presence of ferromagnetic NPs (coercive field, H_c ∼ 2000 Oe at 300 K), is fully contained in a PEO sphere leading to readily discernible magnetic nanodomains (bits).