First-principles study of ferroelectric domain walls in multiferroic bismuth ferrite

Abstract

We present a rst-principles density functional study of the structural, electronic and magnetic properties of the ferroelectric domain walls in multiferroic BiFeO3. We nd that domain walls in which the rotations of the oxygen octahedra do not change their phase when the polarization reorients are the most favorable, and of these the 109 • domain wall centered around the BiO plane has the lowest energy. The 109 • and 180 • walls have a signicant change in the component of their polarization perpendicular to the wall; the corresponding step in the electrostatic potential is consistent with a recent report of electrical conductivity at the domain walls. Finally, we show that changes in the Fe-O-Fe bond angles at the domain walls cause changes in the canting of the Fe magnetic moments which can enhance the local magnetization at the domain walls.

Atomic-scale evolution of modulated phases at the ferroelectric–antiferroelectric morphotropic phase boundary controlled by flexoelectric interaction

“…Local lattice spacing maps were then generated for both Bi/Sm and Fe sublattice (by calculating distances between atoms of the same types), and cation displacement maps were also generated by calculating shifts of the atoms of one type from centres of unit cells formed by atoms of the other type. For BFO, the O sublattice deforms with the Fe sublattice, and thus cation displacement is proportional to polarization [25][26][27] ; in this article, we refer to polarization behaviour when discussing cation displacements. The analysis procedure is illustrated in Fig.…”

Domain wall nanoelectronics

“…Equation (7) shows that, in order to find a ''pure'' (nontwinned) ferroelectric quadrant structure, one will have to look for ferroelectrics with small spontaneous strain and high domain wall energy. BiFeO 3 has a large domain wall energy Lubk, Gemming, and Spaldin, 2009) due to the coupling of polarization to antiferrodistortive and magnetic order parameters (BiFeO 3 is simultaneously ferroelectric, ferroelastic, ferrodistortive, and antiferromagnetic), while at the same time its piezoelectric deformation is small. That helps stabilize closure structures in this material (Balke et al, 2009;Nelson et al, 2011).…”

“…This polar discontinuity means that there is charge density at the walls (see Poisson's equation above). In order to screen this charge density, charge carriers aggregate to the wall, and this carrier increase has been hypothesized to be a cause for the increased conductivity at the domain walls of BiFeO 3 (Seidel et al, 2009;Lubk, Gemming, and Spaldin, 2009). The issue of domain wall conductivity is discussed in greater detail in Secs.…”

180° Ferroelectric Stripe Nanodomains in BiFeO3 Thin Films

“…This is particularly disappointing since the 180° domain walls have been predicted to exhibit the largest band gap reduction and magnetization out of the three possible domain wall variants in BiFeO3. 12,20 Moreover, the structure and properties of 180° ferroelectric domain walls have been extensively studied theoretically in recent years; 20,21 and a non-Ising character of the 180° domain wall, arising from flexoelectric effects, has been proposed. 22 Therefore, experimental verification of the existence of periodic 180° stripe domains in BiFeO3 is important for better understanding the domain formation mechanism, domain wall structure, and its contributions to magnetic and electric properties in this multiferroic material.…”