Intra-wire coupling in segmented Ni/Cu nanowires deposited by electrodeposition

TL;DR

This study investigates the magnetic coupling and switching behavior in segmented Ni/Cu nanowires, revealing how length, diameter, and aspect ratio influence coercive fields and magnetization reversal, with implications for 3D data storage.

Contribution

It provides new insights into intra-wire magnetic coupling mechanisms and demonstrates the creation of nanowire-based spin-valve structures with GMR effects, supported by experimental and simulation data.

Findings

Coercive field depends strongly on nanowire length and diameter.

A transition from coherent rotation to domain wall propagation occurs at aspect ratio ~2.

Nanowire spin-valve structures exhibit giant magnetoresistance due to coupled nanomagnet switching.

Abstract

Segmented magnetic nanowires are a promising route for the development of three dimensional data storage techniques. Such devices require a control of the coercive field and the coupling mechanisms between individual magnetic elements. In our study, we investigate electrodeposited nanomagnets within host templates using vibrating sample magnetometry and observe a strong dependence between nanowire length and coercive field (25 nm to 5 $\mu$m) and diameter (25 nm to 45 nm). A transition from a magnetization reversal through coherent rotation to domain wall propagation is observed at an aspect ratio of approximately 2. Our results are further reinforced via micromagnetic simulations and angle dependent hysteresis loops. The found behavior is exploited to create nanowires consisting of a fixed and a free segment in a spin-valve like structure. The wires are released from the membrane and electrically contacted, displaying a giant magnetoresistance effect that is attributed to individual switching of the coupled nanomagnets. We develop a simple analytical model to describe the observed switching phenomena and to predict stable and unstable regimes in coupled nanomagnets of certain geometries.