Comparison of structural and magnetic properties of La³⁺ substituted BaFe₁₂O₁₉ prepared by different substitution methods

Effect of La³⁺ substitution on structural and magnetic properties of Ba_1−xLa_xFe₁₂O₁₉ (x=0.0–0.2) prepared by two different methods was studied. For the first method, La³⁺ substituted BaFe₁₂O₁₉ has been directly prepared by solid state synthesis of Fe₂O₃ and BaCO₃ at Fe/Ba molar ratio of 6. For the second method, solid state synthesis of Fe₂O₃ and Ba_1−xLa_xFe₂O₄ at molar composition of 5:1 has been adopted. As-prepared powders were characterized by X-ray diffraction, Mössbauer spectroscopy and vibration sample magnetometry. XRD patterns were refined by the Rietveld analysis method. Single phase barium hexaferrite was obtained by both the methods with a minor amount of residual hematite. Ba_1−xLa_xFe₁₂O₁₉ prepared from Ba_1−xLa_xFe₂O₄ showed higher magnetization (M) which was the maximum for x=0.1, without any remarkable change in the coercivity. The increase in M is attributed to increase in hyperfine field for 12k, 4f₁, 4f₂, 2a and 2b sites