Fig. 2. DW displacement and linear wall phase transition.
a Normalized ac Kerr response measured at a segment of a domain wall over a range of frequency (5 Hz–10 kHz) and temperature (40–175 K). A sharp decrease in the Kerr response is noticeable near T = 140 K. b Selected plots of the temperature dependence at constant frequency (horizontal cuts through the frequency-temperature map shown in a). c Measurements of the domain wall displacement plotted against ac magnetic field amplitude at temperatures in the range of 120–140 K (, See Supplementary Fig. 4 for data at higher temperatures). d DW displacement versus temperature. The non-monotonic temperature dependence of the displacement can be understood as a phase transition from a e, circular or f, elliptical wall at low temperatures to a g, linear wall at high temperatures in which the magnetization vanishes at the wall center.