Cobalt-substituted magnetite nanoparticles and their assembly into ferrimagnetic nanoparticle arrays.

A simple process to prepare monodisperse ferrimagnetic cobalt-substituted magnetite Co(x)Fe(3-x)O4 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 H(c) reaching 2.49 kOe.