Colossal Magnetocapacitance Effect and Multiferroism of Polycrystalline   La0.2Pb0.7Fe12O19
  The mutual control of the electric and magnetic properties of a multiferroic solid is of fundamental and great technological importance. We report here on the colossal magnetoelectric coupling effect of polycrystalline La0.2Pb0.7Fe12O19. A large classic ferroelectric hysteresis loop with full saturation and a strong magnetic hysteresis loop were observed simultaneously in polycrystalline La0.2Pb0.7Fe12O19 due to the coexistence of an off-centered FeO6 octahedron in its unit cell and electron spins in the partially filled 3d orbits of the Fe3+ ions. The coupling voltage and capacity demonstrate giant oscillations, along with magnetic field; the maximum magnetocapacitance ratio exceeds 1.9E5 at 80 Hz. The substitution of La ions with Pb ions progressively stabilized the conical spin structure, which gave rise to the spin-current induced capacity oscillations upon magnetic field. 
Guo-Long Tan, Hao-Hao Sheng
cond-mat.mtrl-sci