Abstract
? 2022 Elsevier B.V.The magnetoelectric properties of Bi2Fe4O9 were improved by compounding with BaTiO3. The magnetic results showed enhanced magnetization in Bi2Fe4O9/BaTiO3 composite compared with Bi2Fe4O9, which originated from the substitution of some Fe atoms in the Ti position of BaTiO3. Bi2Fe4O9/BaTiO3 possessed dielectric relaxation in the temperature range of 120–250 K, which was ascribed to the electron hopping process asymmetrically between Fe2+ and Fe3+. Bi2Fe4O9 and Bi2Fe4O9/BaTiO3 composite both exhibited magnetodielectric effects with an applied magnetic field, indicating magnetoelectric coupling. The maximum coupling coefficient Δε/ε in Bi2Fe4O9/BaTiO3 was approximately ? 4.43 % (H = 4000 Oe, f = 0.1 MHz), which was 10 times higher than that of Bi2Fe4O9. The magnetodielectric effects in Bi2Fe4O9 were from the spin-lattice coupling, and the enhanced results in Bi2Fe4O9/BaTiO3 mainly affected by the dielectric relaxation were related to the spin-orbit coupling. In Bi2Fe4O9/BaTiO3, the applied magnetic field altered the energy level of electrons for the Fe2+ (3d6) ion in FeO6 octahedron and then changed the state of electron polarization, which finally gave rise to a change in the dielectric constant. In addition, the stress transfer between the interfaces of Bi2Fe4O9 and BaTiO3 in the composite under a magnetic field also contributed to the magnetodielectric effects.
NSTL
Elsevier