Synthesis and Magnetic Properties of M²⁺Ti⁴⁺ Substituted Ba₁₂Fe₂₈Ti₁₅O₈₄

抄録

  We investigated the synthesis conditions and magnetic properties of M-Ti substituted Ba₁₂Fe₂₈Ti₁₅O₈₄ with initial compositions of Ba₁₂Fe_28-2xTi_15+xM_xO₈₄ (M = Zn, Mg, Ni, Cu, and Co) sintered at 1100-1300°C. The highest substitution amounts of M-Ti for Fe were consistent with the Ti-ion preference of each transition metal site reported before, suggesting that substituted Ti ions also preferred the sites with high Ti-ion occupancies. The spontaneous magnetizations and Curie temperatures were decreased as the substitution amount x was increased, which means that the substitution weakened the super-exchange interactions between Fe-O-Fe. The highest Zn-Ti substitution rate was lower than the other M-Ti substitution rates, which implies that Zn ions tend to enter specific M(2) and M(14) sites in Ba₁₂Fe₂₈Ti₁₅O₈₄. The sweep of the magnetic field from 0 to 80 kOe changed the relative dielectric constant of Ba₁₂Fe₂₈Ti₁₅O₈₄ by 0.283%. This variation of the dielectric constant caused by the application of magnetic fields is not negligible, showing that this compound should be categorized as a multiferroic material.