Synthesis of highly transparent lithium ferrite nanoparticle/polymer hybrid self-standing films exhibiting faraday rotation in the visible region

A lithium ferrite nanoparticle/ethyl(hydroxyethyl)cellulose (EHEC) hybrid was synthesized via in situ hydrolysis of prepolymerized iron(III) 3-allylacetylacetonate (IAA) and lithium acrylate (LA) in the presence of EHEC below 100 °C. The hybrid film was flexible and self-standing and showed high transmittance in the visible region. The crystallite size of lithium ferrite in the hybrid increased from 2.7 to 3.8 nm with decreasing amounts of EHEC. Nanosized lithium ferrite particle/EHEC hybrid showed a BH curve with no remanence at room temperature. The hybrid was superparamagnetic with a blocking temperature of 13 K. The absorption edge of the hybrid film was blue-shifted compared with bulk lithium ferrite. The blue-shift increased with decreasing crystallite size, which was controlled by the amount of EHEC. The self-standing film exhibited a Faraday rotation depending upon the magnetic field. The curve for the specific Faraday rotation (F) versus magnetic field corresponded to that for magnetization versus magnetic field. The figure of merit of the hybrid film was about 3.5 at 700 nm, which was higher compared with those of reported ferrite composite at shorter wavelengths, due to its high transparency.