Efficient in-line skyrmion injection method for synthetic antiferromagnetic systems

Abstract

Although it has been proposed that antiferromagnetically-coupled skyrmions can be driven at extremely high speeds, such skyrmions are near impossible to inject with current methods. In this paper, we propose the use of DMI-induced edge magnetization tilting to perform in-line skyrmion injection in a synthetic antiferromagnetic branched nanostructure. The proposed method circumvents the skyrmion topological protection and lowers the required current density. By allowing additional domain walls (DWs) to form on the branch, the threshold injection current density was further reduced by 59%. The increased efficiency was attributed to inter-DW repulsion and DW compression. The former acts as a multiplier to the effective field experienced by the pinned DW while the latter allows DWs to accumulate enough energy for depinning. The branch geometry also enables skyrmions to be shifted and deleted with the use of only three terminals, thus acting as a highly scalable skyrmion memory block.

Voltage-controlled skyrmion deletion device based on magnetic defects

“…Numerous investigations have been carried out and many methods have been proposed [18][19][20][21][22][23][24]. In particular, the scheme of spin-polarized current injection has shown remarkable applicability to the racetrack memory [18,21].…”

“…However, there are relatively few investigations into the deletion of skyrmions. Several existing schemes, such as the threeterminal device [24] and the spin-polarized current injection [18], are too cumbersome and unreliable in the implementation process. And it is difficult to meet the requirement for data deletion in the racetrack memory.…”

Material systems for FM-/AFM-coupled skyrmions in Co/Pt-based multilayers

“…1(a)), a coupled pair of skyrmions with opposite topological charge (Q = ∓1) and polarity p = ∓1 in synthetic antiferromagnets have been proposed theoretically to reduce the dipolar strayfield in order to make the skyrmions shrink in size and to suppress the SkHE by cancellation of the Magnus force [37][38][39]. Subsequent theoretical papers on AFM-coupled skyrmions in SAF multilayers reported for example on: the method for efficient in-line injection of skyrmions [40], the manipulation of AFM-coupled skyrmions [41,42], and the method to detect the emergence of AFM-coupled skyrmions [43]. The interest in skyrmions in SAF-MMLs surged after the experimental observation of individual 10 nm size AFM-coupled skyrmions at room temperature by Legrand et al [44].…”

Bilayer skyrmion dynamics on a magnetic anisotropy gradient

“…In our work, we derive an analytical model for the dynamics of VCMA gradient-driven skyrmion pair in synthetic antiferromagnetic bilayer structure. The synthetic antiferromagnetic bilayer structure aims to surpass the velocity limit of the monolayer structure due to the skyrmion Hall effect [8,[38][39][40]. A restoring force that is almost ten times greater than the original driving arising from the interlayer exchange coupling raises the maximum possible velocity of skyrmions to the order of km/s.…”