Iron Oxide Shell as the Oxidation-Resistant Layer in SmCo₅@Fe₂O₃ Core–Shell Magnetic Nanoparticles

This paper presents a synthesis of magnetic nanoparticles of samarium cobalt alloys and the use of iron oxide as a coating layer to prevent the rapid oxidation of as-made Sm–Co nanoparticles. The colloidal nanoparticles of Sm–Co alloys were made in octyl ether using samarium acetylacetonate and dicobalt octacarbonyl as precursors in a mixture of 1,2-hexadecanediol, oleic acid, and trioctylphosphine oxide (TOPO). Such Sm–Co nanoparticle could be readily oxidized by air and formed a CoO antiferromagnetic layer. Exchange biasing was observed for the surface oxidized nanoparticles. In situ thermal decomposition of iron pentacarbonyl was used to create iron oxide shells on the Sm–Co nanoparticles. The iron oxide shell could prevent Sm–Co nanoparticles from rapid oxidation upon the exposure to air at ambient conditions.