Magnetic properties and enhanced magneto-dielectric effects in nanobased Bi2Fe4O9

The magnetic and magnetodielectric (MD) properties of nanobased Bi2Fe4O9 are investigated. 2 μm × 2 μm × 300 nm nano-crystals exhibit an anti-ferromagnetic (AFM) transition at 235 K and a weak ferromagnetism in the temperature range of 10–310 K, shown by the magnetic hysteresis loops. The samples show a large MD effect with Δe/e being about −13% at 50 K and 0.45 T, as well as an anomaly of MD effect that increases with increasing magnetic field (H). This large MD effect indicates a strong coupling between the magnetic and dielectric properties in Bi2Fe4O9. Our studies provide strong evidence that both the AFM ordering and ferromagnetism contribute to the MD effects.