Vasylenko I. Obtaining and magnetic properties of nanosized ferrites of Cr, Mn, Co, Ni, and composites based on them

To obtain magnetic nanoparticles (NP) with ferri- and antiferromagnetic order of magnetic moments and magnetic porous composites new methods of synthesis have been developed. The influence of NP size on their magnetic properties was established. It was revealed that NP of ferrites МFe2O4 (M = Mn, Co, Ni) and g-Fe2O3 in size range from 5 to 16 nm are superparamagnetic. With decreasing diameter, the values of the blocking temperature, saturation magnetisation, remanence magnetisation, energy of the magnetic anisotropy barrier decrease, and the values of the magnetic anisotropy constant increase; but nanoparticles CoFe2O4, of size 16 nm, at room temperature exhibit ferrimagnetic properties with high coercive, similar to bulk pattern. It was found that a-(Fe2/3Cr1/3)2O3 nanocrystallites are superparamagnets with low value of magnetisation, in contrast to bulk pattern, which is characterised by antiferromagnetic properties. It was revealed that blocking temperature and magnetisation saturation of Fe3S4 NP are significantly lower than Fe3O4 NP with the same diameter. It was shown that obtained modified magnetic composite can be used for selective sorption of optical isomers of amino acids and saccharides.