Figure 1

(a) $\theta –2\theta$ scans of BFO films grown on different substrates. (b)–(e) Reciprocal-space maps of BFO films grown on STO (b), DSO (c), GSO (d), and NSO (e). (f) Room-temperature OP parameter $c$ as a function of the measured in-plane strain of BFO films grown on different substrates. Horizontal error bars include the difference in the IP parameter along $[001{]}_O$ and $[1-10{]}_O$ directions for $[110{]}_O$-oriented substrates.Reuse & Permissions

Figure 2

(a)–(f) OP parameter of BFO films (triangles) and the different substrates (circles) in pseudocubic notation. (g)–(l) Normalized OP parameter of BFO films (after correction of the paraelectric OP contribution) (symbols) and corresponding mean field fits (lines). Data shown in this figure correspond to samples grown on LSAT (a),(g), STO (b),(h), DSO (c),(i), GSO (d),(j), SSO (e),(k), and NSO (f),(l).Reuse & Permissions

Figure 3

OP phase piezoresponse images measured after poling for $\mathrm{BFO}/\mathrm{LSMO}//\mathrm{LSAT}$ (a) and $\mathrm{BFO}/\mathrm{SRO}//\mathrm{DSO}$ (b) at room temperature (RT) (top) and after annealing 723, 823, 923, and 1023 K, and corresponding averaged phase profiles perpendicular to stripes obtained at RT (blue triangle) and after annealing at 1023 K (red circles). Bottom: Rewritten artificial domains after annealing. (c) Mössbauer spectra of the $\mathrm{BFO}//\mathrm{GSO}$ film at 298 K (top) and 530 K (bottom). (d) Corresponding hyperfine field evolution (symbols) as a function of temperature together with the mean field fit (line). (e) AFM peak $(\frac{1}{2}\frac{1}{2}\frac{1}{2}{)}_C$ as a function of temperature measured using neutron diffraction on a 400 nm BFO film on STO. The evolution of the peak relative intensity is reported in (f), the line is a guide for the eyes. (f) OP $c$ parameter as a function of temperature of BFO films on STO, GSO, and NSO. Changes in slope, signaled by the linear fits, indicate the second order transition from an AFM to a paramagnetic state at $T_N$.Reuse & Permissions

Figure 4

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 $\omega$ along $x$, $y$, and $z$ axes (${\omega }_X$ and ${\omega }_Y$, red line, and ${\omega }_Z$, blue line). (c) Theoretical results on BFO film transition temperatures ($T_C$, blue line, and $T_N$, green line) as a function of misfit strain. The activation temperatures for the antiferrodistortive oxygen tilting along the $z$ direction (tetragonal distortion $T_{001}$, black line), for the antiferrodistortive oxygen tilting within the $x\mathrm{\text{−}}y$ plane (orthorhombic distortion $T_{110}$, red line), and for the tilting along [$uuv$] direction (monoclinic distortion $T_{uuv}$, orange line) are also plotted. Experimental $T_C$ (circles) and $T_N$ (squares and triangles) values. Vertical error bars for $T_N$ values correspond to symbol size and for $T_C$ values result from maximum variation of $T_C$ that may be obtained between different fitting processes using the mean field function. Below $T_C$, 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 [$u^{\prime }{u}^{\prime }{v}^{\prime }$] axis.Reuse & Permissions