Room-temperature ferromagnetism and ferroelectricity of nanocrystalline La_2Ti_2O_7

摘要

La_2Ti_2O_7 nanocrystalline powders and pellets were prepared by sol-gel method. The nanocrystalline powders present room-temperature ferromagnetism (FM). The vacuum annealing enhances FM, show-ing that the observed room-temperature FM for La_2Ti_2O_7 possibly originates from oxygen vacancies atear surfaces of nanograins. La_2Ti_2O_7 pellets annealed at 1000℃ for 1 h show the coexistence of ferromagnetism and ferroelectricity (FE) at room temperature. Meanwhile, the room-temperature mag-netodielectric (MD) effect was also observed in theLa_2Ti_2O_7multiferroic pellet, indicating the coupling between magnetic and electric properties. The value of Δε_r/ε_r(O) forLa_2Ti_2O_7 multiferroic pellet reaches 39.3% at 1 kHz under H= 6 kOe.