Facilitating electrical and laser-induced skyrmion nucleation with a dipolar-field enhanced effective DMI

TL;DR

This paper experimentally demonstrates that enhancing the effective Dzyaloshinskii-Moriya interaction (DMI) via dipolar fields in multilayers significantly improves skyrmion nucleation and stability, enabling higher density and stronger field resilience.

Contribution

It introduces a method to enhance effective DMI in magnetic multilayers by layer-dependent DMI sign, facilitating improved skyrmion nucleation and stability.

Findings

Skyrmion density increased up to 20 times with enhanced DMI.

Skyrmions observed under stronger magnetic fields, indicating improved stability.

Dipolar field manipulation effectively controls skyrmion nucleation.

Abstract

We demonstrate experimentally how the nucleation of skyrmions in an Ir, Co, and Pt based magnetic multilayer is affected by introducing a layer dependent sign for the Dzyaloshinskii-Moriya interaction (DMI). In one stack, the bottom half of the stack is given a positive DMI and the top half a negative DMI, and as a result, the in-plane component of the dipolar field is aligned parallel to the effective field of the DMI in every layer, enhancing the effective DMI. We show that this enhanced DMI facilitates the nucleation and stability of skyrmions using both current-driven and laser-induced skyrmion nucleation. In the devices with an enhanced effective DMI, the density of nucleated skyrmions is greater by up to a factor 20 and skyrmions can be observed in stronger magnetic fields - suggesting that their stability is also improved. These results show that skyrmion nucleation depends strongly on the magnitude of the effective DMI in a magnetic multilayer and that the dipolar field within such a multilayer presents an effective route towards controlling the effective DMI, and thereby, the nucleation of chiral magnetic textures.