S. Ammar et al., Magnetic properties of ultrafine cobalt ferrite particles synthesized by hydrolysis in a polyol medium, J MAT CHEM, 11(1), 2001, pp. 186-192
Fine CoFe2O4 powders with monodisperse, almost equi-axial nanometer-sized p
articles were synthesised in a polyol medium by forced hydrolysis of ionic
Co(ii) and Fe(iii) salts at 160 degreesC. K(Co) XANES and Fe-57 Mossbauer s
pectroscopy show that the structure of this ferrite is slightly deviated fr
om an inverse spinel structure: 16% of cobalt atoms are in tetrahedral site
s. The particles are superparamagnetic above 300 K and ferrimagnetic below
this blocking temperature with, at low temperature, strong coercivity, a sa
turation magnetisation value close to the bulk value and high reduced reman
ence. The saturation magnetisation measured at 5 K is clearly enhanced with
respect to CoFe2O4 nanometer-sized particles previously prepared by other
methods. These magnetic characteristics suggest that these particles have a
high crystallinity which may result from this novel synthesis route.