Extended properties of magnetic spins of zinc ferrite nanoparticles in the THz frequency range

We fabricated nanoparticles of Zn ferrite of the chemical formula ZnFe$_2$O$_4$ using the auto-combustion technique, and investigated their magnetic spin distribution and frequency response to optical excitation. Optical absorption and magnetic characterization of the nanoparticles were carried out in the UV–Vis and IR range, and extended on the low frequency side down to the THz domain. The nanoparticles were also characterized by X-ray diffraction and by magnetic force microscopy. The optical dielectric constant was calculated in both the UV–Vis and the THz domain. The optical bandgap, the dispersion energy and the oscillator strength of the nanoparticles were calculated from the optical data based on the single oscillator model. We measured the optical absorption, transmission and reflection spectra in the wavelength range from 200 to 800 nm, and calculated the refractive index, absorption and extinction coefficient. The optical band gap was found to be 1.14 eV and the oscillating energy of the dipole was determined to be 6.94 eV. The study shows that the coordination number of a metal complex and the symmetrical arrangement play an important role in determining the nanoparticle properties