Compositional control and millimeter wave properties of micro-/nano-sized M-type barium hexaferrite BaFe12O19 synthesized by hydrothermal method

Ferrites with hexagonal crystal symmetry have received much scientific and technological attention in their centimeter-/or even millimeter- (mm-) wave applications, since the hexagonal crystal symmetry leading to high magnetocrystalline anisotropy energies and subsequently high ferromagnetic resonance frequencies, among the most popular microwave hexaferrites are those derived from the M-type barium hexaferrite BaFe₁₂O₁₉ [1]. There has been an increasing interest in the hydrothermal synthesis of hexaferrites recently, as it is a relatively economic and simple way of making ferrite nanoparticles. Although the as-synthesized product contains hexaferrites at synthesis temperatures <;250, it is often a mixed phase or chemically in homogeneous, and usually needs subsequent annealing to make a pure phase hexaferrites product [2,3]. In this work, BaFe₁₂O₁₉ micro/nanopar-ticles were obtained with their composition well-controlled at a relatively low temperature by hydrothermal method, and millimeter wave magnetic properties were investigated in the Ka band region.