Cationic distribution and spin canting in CoFe2O4 nanoparticles

CoFe2O4 nanoparticles (< D-NPD > similar to 6 nm), prepared by a thermal decomposition technique, have been investigated through the combined use of dc magnetization measurements, neutron diffraction, and Fe-57 Mossbauer spectrometry under high applied magnetic field. Despite the small particle size, the value of saturation magnetization at 300 K (M-s congruent to 70 A m(2) kg(-1)) and at 5 K (M-s congruent to 100 A m(2) kg(-1)) are rather close to the bulk values, making the samples prepared with this method attractive for biomedical applications. Neutron diffraction measurements indicate the typical ferrimagnetic structure of the ferrites, showing an inversion degree (gamma(NPD) = 0.74) that is in very good agreement with cationic distribution established from low temperature (10 K) Mossbauer measurements in high magnetic field (gamma(moss) = 0.76). In addition, the in-field Mossbauer spectrum shows the presence of a non-collinear spin structure in both A and B sublattices. The results allow us to explain the high value of saturation magnetization and provide a better insight into the complex interplay between cationic distribution and magnetic disorder in ferrimagnetic nanoparticles.