Skyrmions offer high density, low power, and nonvolatile memory functionalities due to their nanoscale and topologically-protected chiral spin structures. For integrated high-bandwidth devices, one needs to control skyrmion generation and propagation rates using current. Here, we introduce a skyrmion initialization and control method to generate periodic skyrmions from 114 MHz to 21 GHz using spin-polarized direct current. We first initialize a stable magnetic domain profile that is pinned between a notch and a rectangular constriction using a DC pulse. Next, we pass spin-polarized DC charge current to eject periodic skyrmions at a desired frequency. By changing the DC current density, we demonstrate in micromagnetic simulations that skyrmion generation frequencies can be controlled reversibly over more than seven octaves of frequencies. By using domain pinning and current-driven skyrmion motion, we demonstrate a highly tunable and DC-controlled skyrmion signal source, which pave the way towards ultra wideband, compact and integrated skyrmionic circuits.

Nanoscale skyrmions enable ultralow-power nonvolatile logic gate designs due to their current-driven motion and topological protection. A key building block in skyrmion-based digital spintronics is the logic inverter (NOT) gate. Despite recent computational and practical demonstrations, a skyrmion-based low-power, wideband, and cascadable inverter gate is still a long way off. For skyrmion-based logic circuits, a systematic design and analysis of an inverter gate is essential. Here we present a skyrmion logic inverter design and analyze its full operation using micromagnetic modeling. Because of the substrate thermal conductivity, our investigations reveal that the all-metallic inverter gate can function with direct current drive, wide bandwidth, submicron footprint, no or low external magnetic field, cascadability, and with room-temperature thermal stability despite Joule heating. Using magnetic insulators for eliminating Joule heating and lowering the exchange stiffness, magnetic moment and other factors might further assist in reducing power consumption by more than four orders of magnitude.

Synthetic antiferromagnetically-coupled (SAF) multilayers provide different physics of stabilizing skyrmions while eliminating topological Hall effect (THE), enabling efficient and stable control. The effects of material parameters, external current drive, and...

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