Hydrothermal synthesis, magnetic and electromagnetic properties of hexagonal Fe3O4 microplates

Magnetite (Fe3O4), with an inverse spinel structure, grows naturally in octahedral shape with eight equivalent {111} crystallographic planes. Here we demonstrated the successful morphology tuning of Fe3O4 microcrystal from the dominant octahedral shape to planar microplate shape by a facile hydrothermal method. The top and bottom surfaces of Fe3O4 microplates obtained under strongly alkaline and reductive conditions were bounded by {111} facets, and the formation of {111} twin planes was thought to be accountable for the anisotropic morphologies. The obtained Fe3O4 microplates delivered saturation magnetization (Ms) of 96.6 emu/g and coercivity (Hc) of 50 Oe. We also measured the electromagnetic properties of Fe3O4 microplates for possible applications as filler for electromagnetic wave absorption coatings.