The effect of transition metal ions on the phase formation during the hydrothermal synthesis of barium hexaferrite

Abstract

In this study, the effect of certain transition metal cations (Cr³⁺, Ni²⁺, Co²⁺ and Mn²⁺) on the hydrothermal synthesis of barium hexaferrite was investigated. It was found that the addition of Co²⁺ and Mn²⁺ significantly promotes the formation of the hexaferrite phase. In other cases, the dominant product of the reaction was the non-magnetic ferrihydrite. The mechanism by which hexaferrite forms in the presence of Co²⁺ or Mn²⁺ was discussed. The hexaferrites obtained in this work were nanoplates with a thickness of no more than 20 nm and a diameter ranging from 80 to 400 nm. These powders had a low saturation magnetization (<20 emu/g) and coercivity (<450 Oe). Although the magnetism of these hexaferrite nanoplates is relatively weak, they can still be manipulated by external magnetic field and could be used to prepare anisotropic hexaferrite materials. Pierre Muller