A manganese zinc ferrite nanoparticle/polymer hybrid nanocomposite was synthesized in situ from metal acetylacetonates at 80 A degrees C. A mixture of manganese(II) acetylacetonate (MA), zinc(II) acetylacetonate (ZA), and iron(III) 3-allylacetylacetonate (IAA) was hydrolyzed and polymerized, yielding a spinel oxide nanoparticle/organic hybrid. The crystallite size of the spinel particles was dependent upon the hydrolysis conditions of MA-ZA-IAA. Crystalline manganese zinc ferrite nanoparticles less than 5 nm in size were uniformly dispersed in the organic matrix. The magnetization of the hybrid increased as the amount of water for hydrolysis increased. The magnetization versus field curve for the manganese zinc ferrite nanoparticle/organic hybrid showed neither remanence nor coercivity above 11 K. The magnetization versus H/T curves from 50 to 200 K were superimposed on the same curve described by the Langevin equation. The remanent magnetization and coercive field of the hybrid were 2.1 emu/g and 20 Oe, respectively, at 4.2 K. The absorption edge of the hybrid film was blue-shifted as compared to that of bulk ferrite.