Mossbauer investigations in hematite nanoparticles

Hematite nanoparticles of average size 20 nm were synthesized using the sol-gel method, and the structural characterizations were conducted using XRD and TEM. The XRD profile revealed a small fraction of the maghemite phase and the main hematite phase. Mössbauer spectroscopy was used to study the magnetic structure of the particles and revealed a third but very slight non-magnetic phase. Mössbauer spectrum shows 35% of the nanoparticles exhibiting superparamagnetism. The weighted average Morin transition temperature for the particles determined by Mössbauer is 262 K, which is remarkably similar to the bulk value and higher than the Morin transition determined by VSM (about 250 K). The reported findings on the hematite nanoparticles will help understand the enhanced ferromagnetic behavior of the hematite nanoparticles at room temperature, which is crucial for potential applications.