Synchronous precessional motion of multiple domain walls in a ferromagnetic nanowire by perpendicular field pulses

June-Seo Kim,Gisela Schütz,Markus Weigand,André Bisig,Felix Büttner,Robert M Reeve,Benjamin Krüger,Mohamad-Assaad Mawass,Hermann Stoll,Tomek Schulz,Mathias Kläui,Chun-Yeol You,Henk J M Swagten,Bert Koopmans,Stefan Eisebitt,Jungbum Yoon

doi:10.1038/ncomms4429

Abstract

Magnetic storage and logic devices based on magnetic domain wall motion rely on the precise and synchronous displacement of multiple domain walls. The conventional approach using magnetic fields does not allow for the synchronous motion of multiple domains. As an alternative method, synchronous current-induced domain wall motion was studied, but the required high-current densities prevent widespread use in devices. Here we demonstrate a radically different approach: we use out-of-plane magnetic field pulses to move in-plane domains, thus combining field-induced magnetization dynamics with the ability to move neighbouring domain walls in the same direction. Micromagnetic simulations suggest that synchronous permanent displacement of multiple magnetic walls can be achieved by using transverse domain walls with identical chirality combined with regular pinning sites and an asymmetric pulse. By performing scanning transmission X-ray microscopy, we are able to experimentally demonstrate in-plane magnetized domain wall motion due to out-of-plane magnetic field pulses.

Highlights

Magnetic storage and logic devices based on magnetic domain wall motion rely on the precise and synchronous displacement of multiple domain walls
As an alternative to current-induced domain wall (DW) motion, we introduce a novel mechanism to move DWs by magnetic fields with the field direction being perpendicular to the in-plane magnetization of the domains and DWs
We extend the one-dimensional collective coordinates model to include the torque generated by the OOP field (which we will show to resemble the effect of the adiabatic spin transfer torque (STT)) and explain how dynamic OOP field pulses can be employed to move DWs

Summary

Introduction

Magnetic storage and logic devices based on magnetic domain wall motion rely on the precise and synchronous displacement of multiple domain walls. In the case of in-plane field-driven DW motion, the direction of the displacement depends on the DW type, that is, head-to-head or tail-to-tail, which in our model is given by the DW handedness cp 1⁄4 þ 1 or cp 1⁄4 À 1, respectively.

Results

Conclusion