Magnetic and optical studies of NiFe2O4 micro and nanoparticles

Abstract

The nickel ferrite micro and nano-particles have been prepared via solid state and sol-gel auto-combustion technique and its single phase formation, cubic spinal crystal structure (space group Fd-3m) and surface morphology was confirmed by XRD, FESEM and TEM techniques respectively. The optical band gap was estimated from reflectance spectra using Kubelka-Munk equation and the direct optical band gap enhances in nanoparticles (1.905 eV) than microparticles (1.805 eV) due to quantum confinement effect. The small value of remanence magnetization (Mr) and coercive field (Hc) of nanoparticles was observed from narrwow hysteresis M-H loop which reccomends its superparamagnetic states near room teperature (296K). The absence of blocking temperature for micro-particles from 0-300 K confirms the non-existance of single-domain region and superparamagnetic states.