Size and shape effect on the canted antiferromagnetism in α-Fe2O3 particles

The effect of thermal treatments on both the Morin transition and the spin flop field (Hsf) of α-Fe2O3 acicular particles (major axis:(350 ± 50) nm; minor axis: (85 ± 15) nm.) has been investigated by means of magnetization vs temperature-magnetic field measurements. Both the Morin transition and the spin flop process have been observed only after an annealing treatment at 500 °C. Due to the finite size effect, the values of the Morin temperature and spin-flop field are significantly below the bulk value.