Narrow Results

M-type SrFe_12-xAl_xO₁₉(0 < x < 2.5) nanoparticles have been synthesized by citrate–nitrite sol–gel technique. The experimental results have shown that Al³⁺ ions substitute Fe³⁺ ions in the sublattice, and the samples remain in the hexagonal magnetoplumbite phase. The saturation magnetization M_s and remanence M_r of M-type SrFe_12-xAl_xO₁₉(0 < x < 2.5) nanoparticles linearly decrease when x increases. x = 0, M_s = 63.5 emu/g and M_s = 23.8 emu/g at x = 2.5 when the magnets are sintered at 1100°C. Meanwhile, the coercivity H_c of the samples fluctuate as doped with Al, and reach maximum H_c = 10.59 kOe when x = 1.5. The intergranular exchange–coupling interactions between the nanoparticles, which are proved by the measurement of Henkel plots (δM), and the interactions become more intensive as the Al substitution x increases.