Field-driven domain wall motion under a bias current in the creep and flow regimes in Pt/[CoSiB/Pt]N nanowires.

Y H Choi,T Ono,M H Jung,C.-Y You,K Lee,K.-J Kim,T W Kim,Y Yoshimura

doi:10.1038/srep23933

Abstract

The dynamics of magnetic domain wall (DW) in perpendicular magnetic anisotropy Pt/[CoSiB/Pt]N nanowires was studied by measuring the DW velocity under a magnetic field (H) and an electric current (J) in two extreme regimes of DW creep and flow. Two important findings are addressed. One is that the field-driven DW velocity increases with increasing N in the flow regime, whereas the trend is inverted in the creep regime. The other is that the sign of spin current-induced effective field is gradually reversed with increasing N in both DW creep and flow regimes. To reveal the underlying mechanism of new findings, we performed further experiment and micromagnetic simulation, from which we found that the observed phenomena can be explained by the combined effect of the DW anisotropy, Dzyaloshinskii-Moriya interaction, spin-Hall effect, and spin-transfer torques. Our results shed light on the mechanism of DW dynamics in novel amorphous PMA nanowires, so that this work may open a path to utilize the amorphous PMA in emerging DW-based spintronic devices.

Highlights

The trend of the domain wall (DW) anisotropy can account for our first finding
We find that there exists finite Dzyaloshinskii-Moriya interaction (DMI) in our samples, but the sign as well as strength of DMI does not significantly depend on N, manifesting that the DMI does not play the main role in the observed phenomena
We investigated the DW motion in two extreme regimes of DW flow and creep motions for the amorphous perpendicular magnetic anisotropy (PMA) multilayer with heavy metals, Ta/Pt/[CoSiB/Pt]N nanowire structure, for different N and w

Summary

Introduction

The trend of the DW anisotropy can account for our first finding Such an enhancement of DW anisotropy suggests that spin waves can be emitted during the DW motion which accelerates the DW motion[23]. The SHE and STT effects are calculated based on the reported material parameters, and it is found that their relative strength gradually changes with increasing N from SHE dominant for low N to STT dominant for high N. This can explain our second finding qualitatively, because the SHE (STT) assists the DW motion along the current (electron) flow direction

Methods

Results

Conclusion