Herein, we report a facile synthesis of iron oxide nanoparticles by a hydrothermal route. The X-ray diffraction
analysis confirms that these nanoparticles are of pure magnetite (Fe3O4) phase. Further, the morphology and
average particle size were investigated using scanning electron microscopy. The average particle size of these
nanoparticles was observed to be ~65 nm. The magnetic measurement reveals the ferromagnetic nature of the
synthesized Fe3O4 nanoparticles at room temperature. The coercivity and remanence magnetization were
observed to be 98 Oe and 0.51 μB/molecule, respectively. Fe3O4 nanoparticles showed a sharp transition (Verwey
transition) around 120 K in M vs. T measurements. The observation of the Verwey transition indicates the high
quality and phase purity of the synthesized Fe3O4. Moreover, the Fe3O4 nanoparticles were electrochemically
characterized for their potential application as an electrode for ultra-capacitors. The specific capacitance of
97 F/g at the current of 1 mA was observed with excellent cyclic stability. The present facile synthesis method
could be a potential approach for fabrication of ultra-capacitors using cheap and environment friendly
ferromagnetic iron oxide nanoparticles for high performance energy materials