Collective skyrmion motion under the influence of an additional interfacial spin-transfer torque

Voltage-controlled magnetic anisotropy gradient-driven skyrmion-based half-adder and full-adder

Spintronic devices have revolutionized the way we process or store information compared to dissipative charge-based electronics. Among various spin-based technologies, skyrmions - topologically protected nano-size spin textures - have emerged as the most promising alternative for future data processing. Here, we have proposed binary adder circuits - central to most digital logic circuits - based on skyrmions. Using micromagnetic simulations, we have demonstrated half-adder and full-adder logic functionalities by precisely driving the skyrmions through voltage-controlled magnetic anisotropy gradient, besides taking advantage of the physical effects such as the skyrmion Hall effect, skyrmion-skyrmion topological repulsion and skyrmion-edge repulsions. The proposed voltage-control-based method of driving the skyrmions is energy efficient compared to the electrical current-driven approach, and it also overcomes the issue of Joule heating. A reliable operation in a wide range of Dzyaloshinskii-Moriya interaction strengths, magnetic anisotropy gradient, and dimensional parameters has been shown, which offers robustness to the device design. The results pave the way for the skyrmion-based computational architecture, which is significant for next-generation non-volatile data processing.

Dynamic Motion of Polar Skyrmions in Oxide Heterostructures

Polar skyrmions have been widely investigated in oxide heterostructures due to their exotic properties and intriguing physical insights. However, the field-driven motion of polar skyrmions, akin to that of the magnetic counterpart, remains elusive. Herein, using phase-field simulations, we demonstrate the dynamic motion of polar skyrmions with integrated external thermal, electrical, and mechanical stimuli. External heating reduced the spontaneous polarization, while an applied electric field decreased the skyrmion size and weakened the interactions between the skyrmions. Together, the skyrmion motion barrier is significantly reduced from 40 to 2 eV under 9 V at 500 K. An applied mechanical force transformed the skyrmions into a c-domain region near the indenter center under the electric field, providing the space and driving force needed for the motion of the skyrmions. This study confirms that polar skyrmions can move like particles and provides concrete design principles for polar skyrmion-based electronic devices.