Investigation of size-dependent electrical, dielectric, and magnetic properties of iron oxide nanostructures

In this article we report magnetite (Fe3O4) nanoparticles prepared via hydrothermal technique at different reaction time and precursor's concentration. X-ray diffraction (XRD) result shows the formation of single phase iron oxide that matches well with standard JCPDS card #: 01-079-0418. Excellent crystallinity was achieved for octahedral shape particles (-150 nm) as compared to porous spherical shape Fe3O4 particles (-250 nm) which is supported by field emission scanning electron microscope images (FESEM). Fourier transform infrared spectroscopy (FTIR) results show strong peak at 540 cm -1 for both samples indicating Fe-O-Fe bending vibration and formation of chemical bonding characteristic of Fe3O4 lattice structure. The electrical transport properties show that correlated barrier hopping (CBH) between Fe3+ and Fe2+ ions, is the possible operating conduction mechanism in both samples and octahedral shape Fe3O4 nanoparticles are more conductive than porous spherical shape particles. The corresponding activation energies of grain and grain boundary for octahedral and porous spherical shape Fe3O4 nanoparticles are -0.197 & -0.292eV and -0.226 & -0.30eV, respectively. Furthermore, dielectric constant of the octahedral shape Fe3O4 nanoparticles is high due to its low energy losses and high value of crystallinity as compared to spherical shape particles. Magnetic properties show ferrimagnetic nature of both Fe3O4 samples. Corresponding high values of magnetic saturation, coercivity, and remanent magnetization of octahedral shape Fe3O4 particles are 71emu/g, 123 Oe, and 10.6 emu/g, respectively, which indicates the influence of magnetic properties on the grain size, crystallinity and morphology of the constituent particles.