Structural, IR, and Magnetic Studies of Annealed Li-Ferrite Nanoparticles

Nanoparticles of spinel Li-ferrite, Li0.5Fe2.5O4, were prepared by sol-gel autocombustion technique and annealed at different temperatures (T (a) = 673, 873, and 1073 K), i.e., at relatively low annealing temperatures to control the crystallite size. The saturation magnetization (M (s)) increased, and the surface area decreased by increasing the crystallite size, while Curie temperature (T (C)) remained almost constant. The critical crystallite size (D (s)), 74 nm, which corresponds to a maximum value of coercivity was determined. Samples with crystallite sizes a parts per thousand currency sign D (s) had low initial permeability mu(i), while the other samples lying in the multidomain region showed very high mu(i) values indicating a reversible domain wall displacement mechanism. Hence, the crystallite size plays an important role in changing the physical and magnetic properties of Li-ferrite.