Stabilizing skyrmions in stepped magnetic devices for multistate memory

TL;DR

This paper explores how to stabilize and control magnetic skyrmions in nano-tracks with multiple confinements, enabling multistate memory devices by manipulating skyrmion motion and pinning using spin transfer torque.

Contribution

It demonstrates methods to pin and stabilize skyrmions in specific confinements and shows the potential for multistate memory devices with controlled skyrmion positioning.

Findings

Skyrmions can be pinned and stabilized with specific current pulses.

Single skyrmions are confined to one state, enabling multistate memory.

Multiple skyrmions can be controlled to occupy distinct states without overlap.

Abstract

The dynamics and stability of magnetic skyrmions within a nano-track with multiple confinements are investigated. Firstly, the motion of a single skyrmion under spin transfer torque (STT) is studied. By accurately adjusting the current pulse magnitude and width, the study reveals the possibility to pin and stabilize the skyrmion in each confinement. Due to the Hall angle, the depining of the skyrmion from the top confinement requires two pulses with adjustable time delay while a single pulse is enough to depin it for the case of bottom confinement. In the case of two skyrmions, once one is pinned in one confinement, the second one stabilizes in the nearest available empty state and no more than one skyrmion could be seen in single confinement. Finally and for further confirmation of this behavior, the motion of a large number of skyrmions is investigated under the same conditions. The results show that a multistate device could be obtained with still the existence of only one skyrmion per state. The skyrmions could be displaced along the nano-track until their annihilation at the end of the device.