First-Principles Study of Oxygen Octahedral Tilt Domain Walls in Bismuth Ferrite
Yun-Wen Chen1*, Jer-Lai Kuo1
1Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
* presenting author:Yun-Wen Chen,
Bismuth Ferrite (BiFeO₃) is one of the few perovskite materials, which still possesses its multiferroics at room temperature. Its ground state forms a R3c rhombohedral crystal with G-type antiferromagnetic arrangement on Fe atoms. Because of the recent fabrication technology making the growth of perovskite thin films with only few nanometers possible, various phase transitions or domain walls were observed in experiments due to reasons like strains, doping, and also defects. Besides the traditional ferroelectric domain walls (the discontinuity of electric polarization), the disorder of oxygen octahedral tilts could also be a degree of freedom to form domain walls in the R3c rhombohedral crystal lattice. However, the direct observation of oxygen octahedral tilts is still hard in experiments; hence the existing patterns of oxygen octahedral tilts are not very clear except theoretical predictions. With first-principles modeling, we study the oxygen octahedral tilt domain walls of (001), (011), and (111) planes. Comparing the structure parameters (Bi-Fe distances, Fe-O bond lengths, angles of octahedral tilts …), magnetization, and projected density of states with the counterparts of ferroelectric domain walls, we offer another possible explanation to the observed conductivity variations of J. Seidel’s work. [1],[2]

[1] J. Seidel et al., Nature Mater. 8, 229 (2009).
[2] A. Lubk, S. Gemming, and N. A. Spaldin, Phys. Rev. B 80, 104110 (2009).

Keywords: Bismuth Ferrite, Perovskite, Multiferroics, Domain wall, First-principles