Abstract
Skyrmion, a topologically-protected soliton, is known to emerge via electron spin in various magnetic materials. The magnetic skyrmion can be driven by low current density and has a potential to be stabilized in nanoscale, offering new directions of spintronics. However, there remain some fundamental issues in widely-studied ferromagnetic systems, which include a difficulty to realize stable ultrasmall skyrmions at room temperature, presence of the skyrmion Hall effect, and limitation of velocity owing to the topological charge. Here we show skyrmion bubbles in a synthetic antiferromagnetic coupled multilayer that are free from the above issues. Additive Dzyaloshinskii-Moriya interaction and spin-orbit torque (SOT) of the tailored stack allow stable skyrmion bubbles at room temperature, significantly smaller threshold current density or higher speed for motion, and negligible skyrmion Hall effect, with a potential to be scaled down to nanometer dimensions. The results offer a promising pathway toward nanoscale and energy-efficient skyrmion-based devices.
Highlights
Skyrmion, a topologically-protected soliton, is known to emerge via electron spin in various magnetic materials
On the other hand, large DzyaloshinskiiMoriya interaction (DMI) induced at Pt and W interfaces with the same chirality decreases the formation energy of domain walls (DWs), leading to stable multi-domain states at room temperature
We have shown a formation of synthetic antiferromagnetic (SyAF) skyrmion bubbles at room temperature, which can be moved by spin-orbit torque (SOT) with negligible skyrmion Hall effect (SkHE) and much faster speed for a given current density than ferromagnetic systems
Summary
A topologically-protected soliton, is known to emerge via electron spin in various magnetic materials. The magnetic skyrmion can be driven by low current density and has a potential to be stabilized in nanoscale, offering new directions of spintronics. There remain some fundamental issues in widely-studied ferromagnetic systems, which include a difficulty to realize stable ultrasmall skyrmions at room temperature, presence of the skyrmion Hall effect, and limitation of velocity owing to the topological charge. Additive Dzyaloshinskii-Moriya interaction and spin-orbit torque (SOT) of the tailored stack allow stable skyrmion bubbles at room temperature, significantly smaller threshold current density or higher speed for motion, and negligible skyrmion Hall effect, with a potential to be scaled down to nanometer dimensions. We show SkHE-free motion of skyrmion bubbles at room temperature in synthetic antiferromagnetic (SyAF) systems, which can be driven with much smaller current density than ferromagnetic skyrmion bubbles. The achieved favorable properties are attributed to the employed stack structure which is engineered so that the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction[21], DMI, and SOT act in a concerted way efficiently
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