The effect of misfit strain on properties of epitaxial ${\mathrm{BiFeO}}_3$ films that are grown along the pseudocubic $[\overline{1}10]$ direction, rather than along the usual [001] direction, is predicted from density-functional theory. These films adopt the monoclinic $Cc$ space group for compressive misfit strains smaller in magnitude than $\simeq 1.6\%$ and for any investigated tensile strain. In this $Cc$ phase, both polarization and the axis about which antiphase oxygen octahedra tilt rotate within the epitaxial plane as the strain varies. Surprisingly and unlike in (001) films, for compressive strain larger in magnitude than $\simeq 1.6\%$, the polarization vanishes and two orthorhombic phases of Pnma and $P{2}_1{2}_1{2}_1$ symmetry successively emerge via strain-induced transitions. The Pnma-to-$P{2}_1{2}_1{2}_1$ transition is a rare example of a so-called pure gyrotropic phase transition, and the $P{2}_1{2}_1{2}_1$ phase exhibits original interpenetrated arrays of ferroelectric vortices and antivortices.

• Received 10 May 2011

DOI:https://doi.org/10.1103/PhysRevLett.107.117602