Speaker
Description
Magnetoelectricity, accounting for the coupling between electric and magnetic dipoles, has attracted a revived interest in the last few decades. The interest was largely fueled by the renaissance of multiferroicity where coexisting electrical and magnetic degrees of freedom may couple, as indeed happens in type-II multiferroics displaying an electric polarization induced by a symmetry-breaking modulation of the magnetization. Spatially localized magnetic structures such as domain walls or Skyrmions may also sustain a net electric dipole moment ultimately arising from magnetoelectric coupling, in principle enabling their control via electric field. In this respect, magnetoelectric effects can play an important role in two-dimensional magnets, where a moderate voltage is sufficient to produce a huge electric field perpendicular to the 2D magnet layer. Despite being spatially localized, topological magnetic solitons typically extend over length scales of at least several nanometers, leaving them beyond reach of direct ab initio calculations. To solve this critical issue, we developed a multiscale approach to magnetoelectricity that bridges atomistic and continuum models, with all parameters fully determined from first principles. We carefully validate and apply our approach to the prototypical 2D ferromagnet CrI$_3$, studying the electric polarization of different realizations of spin spirals as well as of magnetic topological solitons in the form of domain walls and Skyrmions or anti-Skyrmions. After providing general symmetry requirements for the magnetoelectric coupling tensor in both atomistic and continuum model, we formally show that the magnetoelectric parameters of our models are equivalent to electric-field induced Dzyaloshinskii-Moriya interactions, further allowing us to address electric-field stabilization of non-collinear spin structures.
