Imaging of a multiferroic domain wall in a non-multiferroic environment

Compared with the surrounding bulk, the domain walls of materials exhibiting spontaneous long-range order exhibit significant changes in properties. The conducting domain walls in ferroelectrics are of great interest, for example, for their potential in rewriteable electric circuits. In contrast, it is rarely discussed that a ferroic material may also exhibit ferroic phases that are stable in the domain walls but not in the surrounding bulk material. Using Faraday rotation microscopy and second harmonic generation, we show that the domain walls in the antiferromagnetic and non-polar phase of ${\text{Dy}}_{0.7}{\text{Tb}}_{0.3}\text{Fe}{\text{O}}_3$ carry spontaneous magnetization and spontaneous polarization. By optical deconvolution, we find a stable width, magnetization, and polarization, supporting the wall-like nature. Magnetic domain formation within the walls is visualized, and magnetic and electric wall-domain switching is concluded from field-poling experiments. With our study, we thus provide visual evidence of the existence of multiferroic domain walls in a non-multiferroic environment.