Highly ordered ultralong magnetic nanowires wrapped in stacked graphene layers

Abstract

SummaryWe report on the synthesis and magnetic characterization of ultralong (1 cm) arrays of highly ordered coaxial nanowires with nickel cores and graphene stacking shells (also known as metal-filled carbon nanotubes). Carbon-containing nickel nanowires are first grown on a nanograted surface by magnetron sputtering. Then, a post-annealing treatment favors the metal-catalyzed crystallization of carbon into stacked graphene layers rolled around the nickel cores. The observed uniaxial magnetic anisotropy field oriented along the nanowire axis is an indication that the shape anisotropy dominates the dipolar coupling between the wires. We further show that the thermal treatment induces a decrease in the coercivity of the nanowire arrays. This reflects an enhancement of the quality of the nickel nanowires after annealing attributed to a decrease of the roughness of the nickel surface and to a reduction of the defect density. This new type of graphene–ferromagnetic-metal nanowire appears to be an interesting building block for spintronic applications.

Diffusion, Nucleation, and Self-Optimization in the Forming Process of Graphene in Annealed Nickel–Carbon Alloy

“…Simulation models were built on the basis of some experimental results. In previous research, El Mel et al 31 and Tosic et al 21 produced graphene layers by annealing Ni−C systems in experiments, and Peng et al 20 demonstrated that the flat surface favors the formation of large graphene; thus, the flake Ni−C model, which has a large and flat surface, was built and optimized. As shown in Figure 1, the initial models of Ni− C alloys were built by randomly replacing nickel atoms with carbon atoms.…”

Fabrication of polymer nanowires via maskless O2plasma etching

“…The base-level nanostructures of a larger dimension can be prepared by using a lithographic method, such as laser interference lithography. Among various nanolithography techniques, laser interference lithography is one of the most efficient optical lithography techniques to create uniform nanopattern arrays over a large substrate area (wafer-level) with good control of the pattern periodicity [23,24], allowing many new applications in nanofabrication with superior simplicity and convenience [25][26][27][28][29][30][31][32][33][34]. In this optical lithography, vertical standing wave effects due to reflection of the incident light from the substrate surface cause serious scalloping profiles along the sidewalls of the patterned photoresist structures [35].…”

Designing magnetic superlattices that are composed of single domain nanomagnets

“…This may shed light on the complexity of the behavior of these unique and extremely interesting magnetic systems. Also, hybrid structures of ferromagnetic superlattices, combined with two-dimensional materials such as graphene and silicene have the potential to revolutionize spin-injection and detection devices for spintronics [ 27 – 30 ]. The ferromagnetic materials are ideal contacts for creating these spintronic devices on, for example, a single layer of graphene [ 29 ].…”