Mossbauer and magnetisation studies of CoFe2O4 particles in a magnetic fluid

The superparamagnetic relaxation and surface phenomena for non-interacting ultrafine cobalt ferrite particles (with an average size of 3.3 nm) dispers ed in a hydrocarbon carrier were studied by Fe-57 Mossbauer spectrometry an d static magnetic measurements as a function of temperature (4-300 K) and a pplied field. It has been shown that at the surface of particles the non-co llinear spin structures exist which essentially modify the magnetic propert ies of CoFe2O4 particles. (C) 2000 Elsevier Science B.V. All rights reserve d.