Magnetism of Magnetite nanoparticles as determined by Mössbauer Spectroscopy

Fe₃O₄ [Magnetite] nanoparticles have magnetism that differs greatly from their bulk counterparts. Whereas bulk Fe₃O₄ is a ferrimagnet, single-domain Fe₃O₄ nanoparticles have been found to be superparamagnetic. This allows for increased magnetization of the nanoparticles compared to the bulk when in a magnetic field. For most paramagnets, magnetization requires applied fields of a few Tesla at low temperatures. This is achievable through the application of superconducting magnets. In superparamagnets, the high susceptibility of the particles allows magnetization through a Nd-Fe-B permanent magnet at room temperature. This is caused by an increased number of magnetic atoms within the particles, which greatly increases susceptibility of the particles. ⁵⁷Co [Cobalt-57] Mössbauer Spectroscopy allows the probing of the internal environment of an iron nucleus, which gives insight into the magnetic properties of the Fe₃O₄ nanoparticles.