Two-Step Magnetization Reversal FORC Fingerprint of Coupled Bi-Segmented Ni/Co Magnetic Nanowire Arrays.

Javier García Fernández,Víctor De La Prida Pidal,Kornelius Nielsch,Andy Thomas,Víctor Vega Martínez

doi:10.3390/nano8070548

Javier García Fernández, Víctor De La Prida Pidal + Show 3 more

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https://doi.org/10.3390/nano8070548

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Abstract

First Order Reversal Curve (FORC) analysis has been established as an appropriate method to investigate the magnetic interactions among complex ferromagnetic nanostructures. In this work, the magnetization reversal mechanism of bi-segmented nanowires composed by long Co and Ni segments contacted at one side was investigated, as a model system to identify and understand the FORC fingerprint of a two-step magnetization reversal process. The resulting hysteresis loop of the bi-segmented nanowire array exhibits a completely different magnetic behavior than the one expected for the magnetization reversal process corresponding to each respective Co and Ni nanowire arrays, individually. Based on the FORC analysis, two possible magnetization reversal processes can be distinguished as a consequence of the ferromagnetic coupling at the interface between the Ni and Co segments. Depending on the relative difference between the magnetization switching fields of each segment, the softer magnetic phase induces the switching of the harder one through the injection and propagation of a magnetic domain wall when both switching fields are comparable. On the other hand, if the switching fields values differ enough, the antiparallel magnetic configuration of nanowires is also possible but energetically unfavorable, thus resulting in an unstable magnetic configuration. Making use of the different temperature dependence of the magnetic properties for each nanowire segment with different composition, one of the two types of magnetization reversal is favored, as demonstrated by FORC analyses.

Highlights

The continuous growth of the nanotechnology makes the understanding of nature at such low scale necessary to develop more advanced devices
The magnetization reversal mechanism of bi-segmented nanowires composed by long Co and Ni segments contacted at one side was investigated, as a model system to identify and understand the First Order Reversal Curve (FORC) fingerprint of a two-step magnetization reversal process
The resulting hysteresis loop of the bi-segmented nanowire array exhibits a completely different magnetic behavior than the one expected for the magnetization reversal process corresponding to each respective Co and Ni nanowire arrays, individually

Summary

Introduction

The continuous growth of the nanotechnology makes the understanding of nature at such low scale necessary to develop more advanced devices. It is a challenge to measure and define the main parameters that represent the population of the fabricated nanostructures In this context, self-ordered porous Anodic Aluminum Oxide membranes (AAOs) when used as templates, have been established as a large scale, suitable and low cost fabrication technique of a wide range of nanomaterials such as antidot thin films, nanotubes and nanowires, among others [1,2,3,4]. Among the applications in other research fields such as photonics, electronics and sensing devices, ferromagnetic nanowires are interesting for high density magnetic data storage and spintronics [7] The latter application has been a subject of extensive study and requires the control of magnetic domain walls and magnetization reversal processes of the nanomaterial. It is still a challenge to extrapolate individual magnetic behaviors of complex nanowires systems from the macroscopic magnetic characterization of the whole nanowire array

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