Structural analysis and magnetic properties of Gd-doped Li-Ni ferrites prepared using rheological phase reaction method

A series of Gd-doped Li-Ni ferrites with the formula of LiNi0.5GdxFe2-xO4 where x = 0.00 similar to 0.08 in steps of 0.02, were prepared by thermolysis of oxalate precursors obtained by rheological phase reaction. The structure, morphology, and the magnetic properties of the samples were characterized by powder X-ray diffraction (XRD), atomic force microscopy (AFM) and a vibrating sample magnetometer (VSM). A single spinel phase was obtained in the range of x = 0.00 similar to 0.04. The lattice parameters of the Gd-doped samples were larger than that of pure Li-Ni ferrite, and increased in the range of 0.00 <= x <= 0.04, then decreased up to x = 0.08, because of the formation of the secondary phase (Gd-FeO3). All samples were spheric particles with an average size of about 100 nm, but agglomerated to some extent. The hysteresis loops indicated that the saturation magnetization decreased gradually with increasing Gd content, while the variation of coercivity was related to the microstructure of the Gd-doped samples.