Abstract
We report on the influence of pinning potentials on current-driven skyrmion dynamics and demonstrate that skyrmions can be gated via either magnetic or electric fields. When encountering pinning potentials, skyrmions are well known to simply skirt around them. However, we show that skyrmions can be depinned much more easily when their driving force is oriented against the pinning site rather that the intuitive option of being oriented away. This observation can be exploited together with the normally undesirable Magnus force for the creation of a skyrmion diode. The phenomenon is explained by the increased skyrmion compression resulting from the spin transfer torque opposing the repulsive potential. The smaller skyrmion size then experiences a reduced pinning potential. For practical low-power device applications, we show that the same skyrmion compression can be recreated by applying either a magnetic or electric field. Our analysis provides an insight on the skyrmion dynamics and manipulation that is critical for the realization of skyrmion-based transistors and low-power memory.
Highlights
Magnetic skyrmions are topologically stable spin textures that have been found in materials with Dzyaloshinskii-Moriya (DM) interaction such as multilayers where the DM interaction arises from the broken inversion symmetry at the interfaces[1,2]
We demonstrate that the pinning potential and subsequently, the skyrmion motion, can be gated through voltage-controlled magnetic anisotropy (VCMA) or external magnetic field at pinning potentials introduced by adding patterned ferromagnetic layers
The ferromagnetic layers act as potential barriers due to the strong topological repulsion between the skyrmions and the ferromagnetic layers
Summary
Modulation received: 19 August 2015 accepted: 18 January 2016 Published: 17 February 2016. There are obstacles that hinder the realization of skyrmion-based memory devices Due to their topological stability, they are highly resistant to conventional pinning used in domain wall devices as they are known to skirt around the pinning sites. The ferromagnetic layers act as potential barriers due to the strong topological repulsion between the skyrmions and the ferromagnetic layers In such systems, we found that skyrmions depin much more when driven against the pinning site due to a skyrmion compression mechanism. By being able to modulate the pinning strength through a field-based method, the device toggles between a high thermal stability state and an efficient driving state at almost no energy cost This unique behavior in our proposed skyrmion pinning structure is critical for the realization of skyrmion-based magnetic transistors and low-power skyrmion channel memory
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