Synthesis and physicochemical properties of magnetic Fe<SUB>3</SUB>O<SUB>4</SUB> particles doped with Gd(III)

Magnetic Fe3O4 nanoparticles were synthesized by alkaline precipitation of aqueous solutions of divalent and trivalent iron salts. Synthesis of Fe3−xGdxO4 nanoparticles (x = 0.05; 0.1) was performed by adding a calculated amount of Gd(NO3)3 6H2O to the initial solution of iron salt mixture. The phase composition and magnetic properties of the synthesized powders were investigated by X-ray phase analysis, Mössbauer spectroscopy on 57Fe isotope and magnetometry at temperatures T = 7, 20 and 300 K. The investigations confirmed the formation of nanoparticles of non-stehiometric Fe3−δO4 magnetite, as well as magnetite doped with Gd3+ ions. The correlation between the average diameter of nanoparticles of the initial Fe3−δO4 powder and doped Fe3−xGdxO4 powder and the salt used in the synthesis, as well as the concentration of Gd (x), respectively, was revealed.