Figure 1.
Effective Hamiltonian results evaluated in a BFO film, at 300 K and as a function of misfit strain; (a) tetragonality (c/a ratio) and (b) antiferrodistortive angles ω along the x-, y- and z-axes (ωX and ωY, red line and ωZ, blue line). (c) Theoretical results on BFO film transition temperatures as a function of misfit strain. The activation temperatures for the antiferrodistortive oxygen tilting along the z-direction (tetragonal distortion T001, black line), for the antiferrodistortive oxygen tilting within the x–y plane (orthorhombic distortion T110, red line), and for the tilting along a [uuv] direction (monoclinic distortion Tuuv, orange line) are also plotted. Experimental TC (circles) and TN (squares and triangles) values. Vertical error bars for TN values correspond to symbol size and for TC values result from maximum variation of TC that may be obtained between different fitting processes using the mean field function. Below TC, for any considered strain, the simulations predict that the crystallographic phase is Cc, with a polarization along a [uuv] direction while the oxygen octahedra rotate about a [u′u′v′] axis. Adapted from [24]. (Online version in colour.)