Geometrically designed domain wall trap in tri-segmented nickel magnetic nanowires for spintronics devices

Farzad Nasirpouri,Manuel Vazquez,Cristina Bran,Eider Berganza Eguiarte,Aristotelis Patsopoulos,Dimitris Kechrakos,Seyed-Majid Peighambari-Sattari,Ester M Palmero

doi:10.1038/s41598-019-45553-w

Abstract

“Domain wall traps” have been engineered and well-exploited in nanostrips by creating a geometrical trapping site, e.g. a single notch along a stripe, compared to diameter-modulated (DM) cylindrical magnetic nanowires (NWs) where multi-segmented DM-NWs have been generally studied. Here, we report our systematic study on the magnetization behavior, domain wall structure and its nucleation/propagation in tri-segmented diameter-modulated Ni nanowires, a simple system to investigate the magnetization reversal as function of segment geometry and lay-out order. We find out that the magnetization behavior of single Ni DM-NWs exhibits the significance of positional ordering of thick and thin segments, distinguished by two distinct geometries including: dumbbell-type (type I) and rolling pin-type (type II). Based on experimental and theoretical simulations, it was evidenced that the wide-narrow junctions create trap sites for domain walls where the narrow segment restricts their motion. This type of geometrically engineered nanowires exhibit potential efficiency for future novel spintronic devices in particular when assembled in arrays of DM-NWs as a practical three-dimensional memory device.

Highlights

In recent years, particular attention is paid to three-dimensional (3D) magnetic nanostructures as excellent candidates for magnetic storage device applications owing to the control of their magnetization reversal modes
It is relevant to the main objective of the present study since it allows us to conclude that the magnetization reversal is driven by the propagation of a single domain wall, not as due to random and uncorrelated movements of walls
It was successfully demonstrated that by engineering the geometry and dimensions of modulating segments, the entire magnetization reversal as well as the initial reversal event can be localized on the junction of thicker-thinner segments

Summary

Introduction

Particular attention is paid to three-dimensional (3D) magnetic nanostructures as excellent candidates for magnetic storage device applications owing to the control of their magnetization reversal modes. Two-segmented DM Ni80Fe20 NWs having alternating diameters of 250 and 500 nm but different segment lengths of 2.5 and 6.5 μm were studied by Salem et al.[23] Their magnetization reversal was governed by the nucleation and propagation of a vortex domain wall. The effect of the geometry on magnetic properties of tri-segmented diameter-modulated nanowires, TS-DW-NWs, was investigated by means of experimental methods including magneto-optical Kerr effect (MOKE), magnetic force microscopy (MFM) and Monte-Carlo micromagnetic simulations. Such NW structures are anticipated to motivate the development of domain-wall mediated storage devices with strong control of magnetic domain wall creation and propagation

Methods

Results

Conclusion