Figure 4. FR at different temperatures and the control of PC morphology.

(a–c) MFM image series taken during FR at 230, 190 and 130 K, respectively. The sample was firstly cooled from room temperature to the specified temperatures in zero field. After the field (perpendicular to the film plane) was increased to 4.0 T to fully melt the COI phase, it was then reduced. The dark arrows in a (0.8 and 0.7 T) indicate an example where adjacent COI droplets merge. The dark arrows in b (0.5 T) and c (0.67 T, t=220′) denote sharp discontinuities. The yellow arrows in b (1.0, 0.8 and 0.7 T) highlight the nucleation and growth of a single COI stripe and how it merges with another one. The four images with green frame in c are taken under the same field but at different times as labelled. The insets in a and b are the FFT (17.0 μm⁻¹ × 10.5 μm⁻¹) for the corresponding images. (d–f) Enlarged views of the regions highlighted by the black dashed boxes in a–c, where the domain widths are measured. The irregular shapes of the COI domains in c make the measurement difficult but it is clear that their widths are much larger. The red arrows in c indicate the pin-like FMM domains. (g) The evolution of COI domains with decreasing temperature after they reappear at 1.2 T during FR at 230 K. The growth of a single domain is highlighted by the white boxes. (h) A schematic of the controlled growth of COI domains from the same initial state, by reducing the field or decreasing the temperature. All scale bars are 2 μm and all scanned areas are 8.2 μm × 8.2 μm. The colour scales are 0.3, 0.3, 0.3, 0.4, 0.5 and 0.25 Hz for a, 1.5, 1.5, 1.5, 2.0, 2.0 and 2.0 Hz for b, 4.0, 4.0, 4.0, 4.0, 4.0 and 0.5 Hz for c and 0.4, 0.6, 1.2, 1.6 and 2.0 Hz for g, respectively.