Enhancement of electric polarization in ultrathin half-metallic [BaFeO3]m/[BaTiO3]n superlattices : an ab initio study

Abstract This theoretical study investigated ultrathin [BaFeO 3 ] m /[BaTiO 3 ] n superlattices with varying periodicities m/n from 1 to 4. At structural level, important relaxations occur, resulting in Ti-O, Fe-O, and Ba-O ferroelectric displacements. The Ti-O displacements in our superlattices reached an amplitude of 32.8 % which is larger than its bulk value in BaTiO 3 of 0.125 Å. In addition, Fe-O displacements in the range of [0.043, 0.122] Å appeared in the BaFeO 3 layers of m/n superlattices. The electronic structure analysis revealed a half-metallic character in all m/n systems. A clear dependence between the minority gap and m/n periodicities was observed in the DOS plots. Two categories of superlattices were distinguished from the electric polarization calculations. The first includes 1/1, 2/3, 3/2, and 4/1 with a polarization comparable to the bulk value of BaTiO 3 . The second category includes the 2/1, 1/2, 1/3, 3/1, and 1/4 systems with polarization amplitudes of 30% larger than the BaTiO 3 bulk value. All m/n superlattices remained ferromagnetic. These findings paved the way to new promising applications of those ultrathin superlattices with tunable electronic properties.