Interconversion of multiferroic domains and domain walls

Materials with long-range order like ferromagnetism or ferroelectricity exhibit uniform, yet differently oriented three-dimensional regions called domains that are separated by two-dimensional topological defects termed domain walls\cite{Tagantsev2010,AlexHubert1998}. A change of the ordered state across a domain wall can lead to local non-bulk properties such as enhanced conductance or the promotion of unusual phases\cite{Seidel2009,Meier2012,Farokhipoor2014}. Although highly desirable, controlled transfer of these exciting properties between the bulk and the walls is usually not possible. Here we demonstrate this crossover from three- to two-dimensions for confining multiferroic Dy$_{0.7}$Tb$_{0.3}$FeO$_3$ domains into multiferroic domain walls at a specified location within a non-multiferroic environment. This process is fully reversible; an applied magnetic or electric field controls the transformation. Aside from the aspect of magnetoelectric functionality, such interconversion can be key to tailoring elusive domain architectures such as in antiferromagnets.