Surface effects in α-Fe2O3 nanoparticles studied by ILEEMS and TMS

To understand the particular properties of thin α-Fe2O3 films, hematite nanoparticles with sizes between 20 and 140 nm have been examined by integral low-energy electron Moessbauer spectroscopy (ILEEMS) and transmission Moessbauer spectroscopy (TMS) at room temperature and 80 K. By comparing the results of both Moessbauer variants, surface effects of the Morin transition are studied. The results clearly indicate that the Morin transition takes place at higher temperature in the interior of the particles as compared to the outer layers. It is found that the lowering of the Morin transition is much stronger at the surface of smaller particles.