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Improving Faraday rotation performance with block copolymer and FePt nanoparticle magneto-optical composite

Miles, Alexander; Gai, Yue; Gangopadhyay, Palash; Wang, Xinyu; Norwood, Robert A.; Watkins, James J.

By 12 March 2019No Comments

Optical Materials Express, 2017, vol 7, 6, pp. 2126-2140



Magneto-optical (MO) composites with excellent Faraday rotation (FR) response were fabricated using iron platinum (FePt) nanoparticles (NPs) and polystyrene-block-poly (2-vinyl pyridine) (PS-b-P2VP) block copolymers (BCPs). Gallic acid functionalized FePt NPs with average core diameters (dcore) of 1.9, 4.9, 5.7 and 9.3 nm have been selectively incorporated into a P2VP domain through hydrogen bonding interactions. The use of copolymer templates to selectively arrange the magnetic NPs guaranteed high MO performance with little trade-off in terms of scattering loss, providing a simple strategy to prepare functional materials for MO applications. As a result, Verdet constants of a 10 wt % loaded 4.9 nm FePt NP composite reached absolute magnitudes as high as ~-6 × 104 °/T-m at 845 nm, as determined by FR measurements at room temperature. At the same time, the MO figure-of-merit was as large as −25 °/T in these composites, indicating both excellent MO performance and transparency. The dependence of the nanocomposite FR properties on particle diameter, loading (from 0.1 wt % to 10 wt %) and composite nanostructure were systematically investigated at four infrared wavelengths (845, 980, 1310 and 1550 nm).

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