Figure 3: The Z3-vortex patterns in Ca2.55Sr0.45Ti2O7 and Ca3Mn1.9Ti0.1O7 crystals.
From: Domain topology and domain switching kinetics in a hybrid improper ferroelectric
(a) A 2.2 × 3.9 μm2 mosaic of DF-TEM images were taken using the superlattice g1+ spot (red-circled) of domain FA(i) in a CSTO crystal along [001]T. The coloured arrows represent polarization directions within the domain. (b) The electron diffraction pattern was taken by covering regions FA(i) and FA(ii) showing a 90°-crystallographic-twin relation. The red/blue circled spots were contributed from the orthorhombic distortions of the FA(i) region and the green/yellow ones were from the FA(ii) area. The colour-circled spot located in each DF image is the selected superlattice Bragg spot to light up the corresponding domains at a given orientation. (c) A DF-TEM image of the white rectangular box region was taken using the blue circled superlattice g1− spot. (d) A proposed domain configuration of c. (e,f) DF-TEM images taken using (e) red circle and (f) yellow circle spots corresponding to superlattice g1+ spots in a CMTO crystal. A Z3-vortex network appears, with three DWs meeting at one point and with irregular shaped FE/FA domains. (g) A proposed domain configuration of e. Two types of FA DWs, FAt (blue-dotted) and FAtr (blue-solid), were identified. (h) Polarized optical image of a CMTO crystal showing irregular twin (that is, FA) domains in a hundreds micrometre scale.
