Cobalt‐Substituted Magnetite Nanoparticles and Their Assembly into Ferrimagnetic Nanoparticle Arrays

A simple process to prepare monodisperse ferrimagnetic cobalt-substituted magnetite CoxFe3-xO4 nanoparticles is reported. These ferrimagnetic nanoparticles are readily dispersed in hexane, forming a stable ferrimagnetic nanoparticle dispersion, and allowing easy nanoparticle self-assembly. When assembled under an external magnetic field (5.5 kOe), these nanoparticles show preferred magnetic alignment with their Hc reaching 2.49 kOe.