Observation of a multiferroic domain wall in a non-multiferroic environment*

Ferroic domain walls, the boundaries between regions of different order-parameter orientation, exhibit properties that often differ strongly from those of the surrounding bulk material. These differences include transport, chemical or crystallographic properties. However, not much is known about the ferroic properties inside the domain walls. Cases like non-ferroic domain walls between ferroic domains or vice versa can be imagined. Here, we present the extreme case of a multiferroic domain wall in a non-multiferroic environment in Dy_0.7Tb_0.3FeO₃ (DTFO). Using the combination of Faraday rotation and optical second harmonic generation microscopy, respectively, we show that a net-magnetization and electric polarization are present only inside the wall only, whereas the interior of the domains is neither magnetized nor polarized. By spatial deconvolution of the Faraday- and SHG signal, we determine the width of our multiferroic domain wall to be 1.25 µm with both techniques. Magnetic and electric fields can switch the magnetization and polarization inside the wall, a defining property of ferroic states, and they are also capable of expanding the multiferroic domain wall into a multiferroic bulk domain.