Unfolding Vortices to Topological stripes in a multiferroic

Hexagonal REMnO$_{\mathrm{3}}$ (RE$=$Ho, Er, Tm, Yb, Lu) is an improper ferroelectric where the size mismatch between RE layers and Mn-O layers induces a simultaneous ferroelectric-trimerization structural phase transition [1]. Two distinct domain configurations have been observed in REMnO$_{\mathrm{3}}$ (RE$=$rare earths): vortex domains vs. stripe domains [2]. However, the rapport between those topologically distinct domain patterns has never been studied. We have investigated the transformation process between vortex domains and stripe domains with the variation of temperature and the application of various strains on thin-plate-like crystals. [1] T. Choi \textit{et al.}, Nature Mater. 9, 253 (2010). [2] S. C. Chae \textit{et al}., PRL 108, 167603 (2012).