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

摘要

Nanoparticles of spinel Li-ferrite, Li_(0.5)Fe_(2.5)O_4, 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 ≤ D_s had low initial permeability μ_i, while the other samples lying in the multidomain region showed very high μ_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.