Synthesis of aligned La3+-substituted Sr-ferrites via molten salt assisted sintering and their magnetic properties

M-type hexagonal Sr_1?xLa_xFe₁₂O₁₉ (x=0, 0.05, 0.1, 0.15 and 0.2) ferrites were synthesized in a molten salt matrix to avoid the agglomeration of particles and control grain growth. By eliminating the impurity phase, the influence of rare earth La³⁺ ion substitutions on the lattice structure, morphology and magnetic properties has been investigated. The results show that La³⁺ substitutions have a great influence not only on the grain growth but also on the magnetic orientation. The easy magnetization direction <001> was remarkably enhanced in all substituted powders aligned along a 5 kOe magnetic field. The optimal magnetic properties were obtained via magnetic orientation when the substitution is x=0.15, showing a coercivity of 6.25 kOe, a saturation magnetization of 69.5 emu/g and a remanence ratio of 0.71. This will possibly enable a wide-range application to generate rare earth La³⁺ ion substituted Sr-ferrites for bonded magnets via molten salt assisted sintering.