Magnetic properties and morphology of ultra-small iron oxide nanoparticles

Abstract Maghemite nanoparticles prepared with the modified synthesis method published by Sun et al. 2004 and followed filtering to extract a sample of smallest nanoparticle size were investigated. The 2-5 nm monocrystalline multi-twinned morphology without surface shells observed. Superparamagnetic behavior was detected above temperature 40 K. An exchange bias loop shift ~ 2 mT at 3 K after cooling an external field T suggested low influence spin disorder effect. Mössbauer spectroscopy confirmed two phases different blocking temperatures, maghemite phase as well second one likely originating from disordered component.