Annealing effects on the magnetic properties of nanocrystalline zinc ferrite

Abstract The effects of annealing on the magnetic properties of nanocrystalline ZnFe 2 O 4 have been studied. The as-prepared sample ZnFe 2 O 4 with the particle size of about 3 nm presents a relatively low blocking temperature of about 6 K as derived from the peak of the zero-field-cooled curve measured in a SQUID. Under the effect of annealing, the particle size significantly increases. Up to the annealing temperature of 800°C, the blocking temperature is found to increase with increasing particle size, whereas the (effective) anisotropy constant K A decreases. The latter effect is attributed to the smaller contribution of the surface anisotropy when the particle size increases.