Dynamics of Muliferroic Domain Wall in an External Field

GdFeO₃ is a typical material showing magnetoelectric (ME) effects. It has three order parameters, antiferromagnetic moments of Fe and Gd ions and electric polarization, and they interact with each other. Tokunaga et al. [1] pointed out the presence of composite domain walls (DW), and discussed ME effects related to DW motion as well as DW splitting induced by impurity pinning.
We have studied the dynamics of composite DW in GdFeO₃ driven by either magnetic or electric field based on the time-dependent Ginzburg-Landau equations [2]. One of the two major findings is about the scaling of DW mobility with field strength. The scaling differs between magnetic and electric field drives, and this is due to a parasitic nature of electric polarization. The second finding is the instability of a composite DW, and it splits into a pair of other types of DWs when a driving field exceeds a critical value. This originates in the deformation of DW internal structure, and thus is an
intrinsic dynamical instability. Phase diagram of DW stability is determined in the space of applied field and strength of order parameter interaction.

[1] Y. Tokunaga et al., Nature Mater 8, 558 (2009)
[2] K. Kawahara and H. Tsunetsugu, arXiv:2008.08600, in press in J. Phys. Soc. Jpn.