Fabrication, magnetic properties and self-assembly of hierarchical crystalline hexapod magnetites

We report a facile and surfactant-free solvothermal approach for the shape controlled synthesis of magnetite (Fe3O4). Hierarchical branched hexapod magnetites with various secondary structures can be prepared from ferrocene by using different solvents and tailoring experimental parameters. The as-prepared hexapods were characterized by X-ray diffraction, room temperature Fe-57 Mossbauer spectroscopy, and scanning and transmission electron microscopy. Compared with bulk magnetite, the obtained Fe3O4 hexapods are single crystals and exhibit different ferrimagnetic behavior with relatively high specific saturation magnetization (90-128 emu g(-1)) and large coercivity (223-238 Oe) values depending on their size and morphology. Self-organization of the shape-anisotropic hexapod crystals has been achieved for the first time by evaporation-mediated assembly. The well-defined hexapod Fe3O4 crystals will be attractive as promising building blocks for the bottom-up design of advanced materials and devices which may have applications in many fields.