High-Curie-temperature ferrimagnetism and ferroelectricity in Bi2FeMoO6
  BiFeO3 is the most famous multiferroic material, but its G-type antiferromagnetism is highly desirable to be replaced by strong macroscopic magnetism beyond room temperature. Here we obtain double perovskite Bi2FeMoO6 with R3 (#146) space group by substituting Mo for 50% Fe in BiFeO3. Our first-principles calculated results show that it is a semiconductor with gap reaching to 0.725 eV, its net magnetic moment is 2\mu_B per formula unit, and its ferroelectric polarization is 85\mu C/cm^2. This ferroelctricity is comparable with that of BiFeO3, but here the magnetism is a strong ferrimagnetism with Curie temperature of 650 K. Our first-principles phonon spectra establishes that this R3 phase is stable. Electric polarization and magnetic easy axis are shown to be in pseudo-cubic [111] axis. Our further analysis shows that the multiferroic mechanism is similar to that in BiFeO3. Therefore, this Bi2FeMoO6 can be used to achieve strong macroscopic magnetism and ferroelectricity well above room temperature, being useful for designing new multifunctional materials and devices. 
Peng Chen and Bang-Gui Liu
cond-mat.mtrl-sci