Synthesis of Ultrafine SrFe₁₂O₁₉ Particles with High Coercivity

Abstract
Ultrafine particles of SrFe₁₂O₁₉ have been synthesized by citrate precursor technique. Solid state reactivity studies of citrate precursor lead to the formation of fine particles of SrFe₁₂O₁₉ below 823K. The size and morphology of these particles were studied by SEM. The surface area measured by BET method for5.2nm crystallite is found to be 27.45 m²/g. having particle size 42nm. Ultrafine particles of SrFe₁₂O₁₉ shows interesting magnetic properties which differs from conventional particles and are measured by VSM. The intrinsic coercive force of 6500Oe is observed for ultrafine SrFe₁₂O₁₉ which is close to the theoretical limit and is one of the highest value reported so-far for isotropic SrFe₁₂O₁₉ having 16.5.nm crystallite size. The Tc value for ultrafine particles is found to be around 830K which is larger than the reported value of 748K for bulk materials. Mossbauer spectroscopy have ben explored to study these fine particles for non-collinear spin structure predominantly at the surface compared to the core of the particule.