Characterization of Multiferroic Domain Structures in Multiferroic Oxides

Figure 2

(a) Cloverleaf domain patterns in ferroelectric YMnO₃ [19, 20]. The combination of TEM (bottom grey-scale layer) and conductive atomic force microscopy (top colored layer) images shows six crystallographic domains joining at a defect line with positive and negative polarization (+ and − signs in the conductive atomic force microscopy image, resp.) alternating around the defect. The TEM dark-field image is obtained by using the 1 1 diffraction spot. (b) Contour plot of the free energy of hexagonal YMnO₃, where the six minima correspond to six structural domains. The arrows in the direction of the minima (colored blue and red) indicate the direction describing these states. The red and blue arrows also encode the sign of electric polarization. The dashed arrow connecting two neighboring minima is a lowest-energy domain wall. (c) and (d) Vortex and antivortex configurations correspond to the cloverleaf defect, respectively. The α, β, and γ antiphase domains correspond to the three options for the origin of trimerization.

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