Nanocrystalline zinc ferrite powders with a partially inverted spinel structure were synthesized by high-energy ball milling in a closed container at ambient temperature from a mixture of alpha-Fe2O3 and ZnO crystalline powders in equimolar ratio. From low-temperature and in-field Mossbauer measurements it is revealed that ZnFe2O4 particles prepared are in superparamagnetic state at ambient temperature. A doublet with an average quadrupole splitting of 0.8 nm/s is observed for the as-milled sample at 295 K, which is much larger than that for bulk ZnFe2O4 prepared by traditional ceramic method and that for ultrafine ZnFe2O4 particles prepared by the co-precipitation method. This indicates larger structural defects in the nanometer-sized ZnFe2O4 particles prepared by high-energy ball milling.
Nanostructured Materials, 1999, Vol 12, Issue 1-4, p. 143-146