Skyrmion-Based Dynamic Magnonic Crystal

Abstract

A linear array of periodically spaced and individually controllable skyrmions is introduced as a magnonic crystal. It is numerically demonstrated that skyrmion nucleation and annihilation can be accurately controlled by a nanosecond spin polarized current pulse through a nanocontact. Arranged in a periodic array, such nanocontacts allow the creation of a skyrmion lattice that causes a periodic modulation of the waveguide's magnetization, which can be dynamically controlled by changing either the strength of an applied external magnetic field or the density of the injected spin current through the nanocontacts. The skyrmion diameter is highly dependent on both the applied field and the injected current. This implies tunability of the lowest band gap as the skyrmion diameter directly affects the strength of the pinning potential. The calculated magnonic spectra thus exhibit tunable allowed frequency bands and forbidden frequency bandgaps analogous to that of conventional magnonic crystals where, in contrast, the periodicity is structurally induced and static. In the dynamic magnetic crystal studied here, it is possible to dynamically turn on and off the artificial periodic structure, which allows switching between full rejection and full transmission of spin waves in the waveguide. These findings should stimulate further research activities on multiple functionalities offered by magnonic crystals based on periodic skyrmion lattices.

A microwave field-driven transistor-like skyrmionic device with the microwave current-assisted skyrmion creation

“…The magnetic skyrmion can also be nucleated with the nano-patterning 39 and be converted from a domain-wall pair 25 . For the manipulation of the magnetic skyrmion, one can use the spin current 21,23 , the spin wave [40][41][42][43] , as well as the thermal gradient [44][45][46] to drive the magnetic skyrmion.…”

Skyrmion domain wall collision and domain wall-gated skyrmion logic

“…The injection of a skyrmion with a perpendicular current is not covered here, because it has already been numerically delivered in refs. 19,30,50 . Subsequently, we will examine successively the motion dynamics of a skyrmion, a DW pair, and the coexisting skyrmion and DW pair triggered by an in-plane current.…”

“…Apart from these intriguing features, i.e., the flexibility around defects and the high sensitivity to currents, recently, it was established that moving magnetic skyrmions can bring about an emergent electromagnetic field, 15 and most recently, it was demonstrated that magnetic skyrmions can even be controllably written and erased using a tiny mechanical force exerted by a microtip. 21 Because of these merits, magnetic skyrmions serve as an active platform for searching new phenomena 20,[22][23][24][25] and more importantly as a promising object for building functional devices 18,[26][27][28][29][30][31][32][33] . Compared to conventional DWs, chiral DWs show greatly enhanced mobility owing to the combined action of the DMI and the spin-Hall effect, and thus hold great promise for implementing new families of spintronic devices.…”

“…The spin valve for skyrmion injection is analogous in structure as for DW injection except for the difference in lateral geometry; the detailed skyrmion-injection process has been presented in literatures 19,29,30 and thus is not replicated here. In simulations, we preset a bubble-like spin configuration 61 and relax it to the equilibrium skyrmion for dynamics study.…”

Emergent geometric frustration of artificial magnetic skyrmion crystals

“…There has been tremendous interest in magnetic skyrmions due to their unusual spintronic properties, such as their topological stability which protects them from being hindered by defects [19][20][21] and their current-driven motion with an ultralow depinning threshold current [21][22][23]. In view of these distinct features, magnetic skyrmions are promising candidates for information carriers in a range of applications in spintronics such as race-track memory devices [20,21], skyrmion logic devices [24], or skyrmion magnonic devices [25], so understanding how to systematically control skyrmion configurations and dynamics with nanopatterns has broad relevance. Although numerous efforts have been devoted to manipulating skyrmion motion, there is little work on how to precisely control their position and confinement.…”