Magneto Optical Properties of FeBxFe2−xO4 Nanoparticles

In this study, FeBxFe2−xO4 nanoparticles (NPs) were synthesized by the polyol method. The M–H hysteresis curves exhibit superparamagnetic characteristics that are both coercivity and remanent magnetization values are negligible. The particle size dependent Langevin function was applied to calculate the magnetic particle dimensions around 9 nm. The measured magnetic moments of NPs are in range of (1.52–2.2) µB and almost half or less with respect to 4 µB of bulk Fe ferrite. Magnetic anisotropy was specified as uniaxial and calculated effective anisotropy constants (K eff ) are between 43.3 × 104 and 19.4 × 104 emu/g. The UV–Vis diffuse reflectance spectroscopy and Kubelka–Munk theory were used to determine the optical properties. The estimated optical band gap values (2.15–2.48 eV) of FeBxFe2−xO4 NPs are bigger with respect to reported values (1.88–2.12 eV) for Fe3O4 NPs in the literature. The bigger E g values are mainly attributed to B concentration and partly to quantum confinement effect.