Motion of skyrmioniums with negligible deformation in synthetic antiferromagnets

A skyrmionium is a magnetic texture composed of two skyrmions with opposite winding numbers (Q) and different sizes. Compared to a skyrmion, a skyrmionium can move at a higher velocity. However, a moving skyrmionium may still deform because of the local skyrmion Hall effect resulting from the two skyrmions with opposite Q. In this study, we propose a skyrmionium motion with negligible deformation in a synthetic antiferromagnetic (AFM) medium, composed of a free ferromagnetic (FM) layer with a skyrmionium and a pinned FM layer with uniform magnetization. The suppression of the skyrmionium deformation is due to the enhanced coupling between the inner and outer skyrmion under interlayer AFM coupling. This study paves the way for the development of devices with high stability, high processing speed, and small sizes.