Dynamical Magnetoelectric Phenomena and Gigantic Microwave Diode Effect of Multiferroic Skyrmion Phase

Abstract

Magnetic skyrmions, vortex-like swirling spin textures characterized by a quantized topological invariant in chiral-lattice magnets, are currently attracting intensive research interest. In particular, their dynamics under external fields is an issue of vital importance because its understanding is crucial both for fundamental science and for technical applications. It has turned out that the skyrmions in an insulating magnet Cu_2OSeO_3 exhibit a multiferroic nature with magnetism-induced ferroelectricity. In this article, we discuss that this multiferroic skyrmion phase shows unique coupled oscillation modes of magnetizations and polarizations, which are both magnetically and electrically active, and the intense interference between their electric and magnetic activation processes leads to an unprecedentedly large diode effect on microwaves. The microwave absorption by this skyrmion phase changes up to 〜20% when the incident direction is reversed. Our results demonstrate that the multiferroic skyrmions can be a promising building block for microwave devices.