Interplay between the cation distribution and production methods in cobalt ferrite

Microscopic, element selective structural and magnetic properties of cobalt ferrite produced by sol–gel (SG) and by ball milling (BM) methods were studied with X-ray absorption near-edge structure (XANES) spectroscopy and X-ray emission spectroscopy (XES). All investigated samples exhibit only Fe3+ and Co2+ cations. The relative distribution of the Co2+ and Fe3+ cations in the tetrahedral and octahedral sites depends on the production method of the samples. For the samples presenting a similar but small grain size (<400 nm), the quantity of Co2+ in B-sites of SG sample is less than that in BM sample. These results are in agreement with magnetic measurements, which BM samples exhibit smaller saturation magnetization as compared with those obtained for SG samples. Additionally the coercive field and magnetostriction are larger in BM samples. All these magnetic properties are dependent on annealing parameters (temperature and time). However for samples with large grain sizes their magnetic properties become insensitive to production processes.