Synthesis and magnetic properties of octahedral Fe3O4 via a one-pot hydrothermal route

Magnetite (Fe3O4) particles were prepared by a facile one-step hydrothermal method in assistant of α-Propylene glycol solution (PG). The X-ray diffraction (XRD), FT-IR analysis and the Verwey transition confirmed that as-prepared magnetite particles were pure spinel Fe3O4 without any impurity. Scanning electron microscopy (SEM) showed that the particles have octahedral morphology and the average edge length of these octahedra was about 500 nm. The shape of crystals can be controlled by the growth rates along different directions, and the growth mode of the Fe3O4 octahedron was outlined. The magnetic measurement at room temperature suggested that the saturation magnetization (Ms) and coercivity (Hc) were 87.48 emu/g and 95.6 Oe, respectively. Fe3O4 nanoparticles showed a sharp transition (Verwey transition) at around 120 K, where the magnetic easy axis switches from the <111> to <100> direction. The value of Hc decreased with the increase of the test temperature, resulting from a fact that the effective magnetic anisotropy decreased with the increase of the test temperature.