Solvothermal Preparation and Magnetic Properties of Monodisperse Superparamagnetic Nanosized Ferrites MFe2O4 (M = Mn, Co, Ni)

Monodisperse spherical nanoparticles of MIIFe 2 III O4 (M = Mn, Co, Ni) with controlled diameter (5-20 nm) were synthesized by solvothermal decomposition of [MIIFe 2 III O(CH3CO2)6(H2O)3] complexes in poly- and tetraethylene glycol. The samples were studied by XRD, TEM, and SQUID magnetometry. The nanoparticles have superparamagnetic behavior. The blocking temperature, magnetization, and magnetic anisotropy barrier decrease, while the magnetic anisotropy constant increases with decreasing particle size.