Systematic Control of Ferrimagnetic Skyrmions via Composition Modulation in Pt/Fe 1- x Tb x /Ta Multilayers.

Magnetic skyrmions are topological spin textures that can be used as memory and logic components for advancing the next generation spintronics. In this regard, control of nanoscale skyrmions, including their sizes and densities, is of particular importance for enhancing the storage capacity of skyrmionic devices. Here, we propose a viable route for engineering ferrimagnetic skyrmions via tuning the magnetic properties of the involved ferrimagnets Fe 1 -x Tb x . Via tuning the composition of Fe 1 -x Tb x that alters the magnetic anisotropy and the saturation magnetization, the size of the ferrimagnetic skyrmion ( d s ) and the average density (η s ) can be effectively tailored in [Pt/Fe 1 -x Tb x /Ta] 10 multilayers. In particular, a stabilization of sub-50 nm skyrmions with a high density is demonstrated at room temperature. Our work provides an effective approach for designing ferrimagnetic skyrmions with the desired size and density, which could be useful for enabling high-density ferrimagnetic skyrmionics.