Dynamical magnetoelectric phenomena of multiferroic skyrmions

TL;DR

This paper reviews recent advances in understanding the multiferroic and dynamical magnetoelectric phenomena of skyrmions in insulating chiral magnets, highlighting their unique coupled excitations and potential for electric control.

Contribution

It provides a comprehensive overview of the theoretical and experimental progress on multiferroic skyrmions, emphasizing their coupled oscillation modes and magnetoelectric effects in insulators.

Findings

Skyrmions exhibit multiferroic properties with spin-induced ferroelectricity.

Electromagnon excitations in skyrmions are both magnetically and electrically active.

Interference effects lead to unique magnetoelectric phenomena at microwave frequencies.

Abstract

Magnetic skyrmions, vortex-like swirling spin textures characterized by a quantized topological invariant, realized in chiral-lattice magnets are currently attracting intense research interest. In particular, their dynamics under external fields is an issue of vital importance both for fundamental science and for technical application. Whereas observations of magnetic skyrmions had been limited to metallic magnets so far, their realization was discovered also in a chiral-lattice insulating magnet Cu2OSeO3 in 2012. Skyrmions in the insulator turned out to exhibit multiferroic nature with spin-induced ferroelectricity. Strong magnetoelectric coupling between noncollinear skyrmion spins and electric polarizations mediated by relativistic spin-orbit interaction enables us to drive motion and oscillation of magnetic skyrmions by application of electric fields instead of injection of electric currents. Insulating materials also provide an environment suitable for detection of pure spin dynamics through spectroscopic measurements owing to absence of appreciable charge excitations. In this article, we review recent theoretical and experimental studies on multiferroic properties and dynamical magnetoelectric phenomena of magnetic skyrmions in insulators. We argue that multiferroic skyrmions show unique coupled oscillation modes of magnetizations and polarizations, so-called electromagnon excitations, which are both magnetically and electrically active, and interference between the electric and magnetic activation processes leads to peculiar magnetoelectric effects in a microwave frequency regime.