# Magnetic Nanowires
## 2 Materials and Methods
This single-bath method was successfully used to prepare various multilayered nanowires including Co/Cu, NiFe/Cu, CoNi/Cu and Ni/Cu. Transmission Electron Microscopy (TEM) images of permalloy (Py = Ni\({}_{80}\)Fe\({}_{20}\))/Cu and Co/Cu multilayered nanowires are shown in Figure 3d,e. Over the last decade, several groups also reported on the electrochemical synthesis of parallel arrays of Ni nanotubes within nanopores of anodic alumina oxide and polymer templates [42; 44; 71; 72]. In this method, core-shell Cu/Ni nanocables are first grown in porous templates at a constant deposition potential, followed by the selective electrochemical etching of the Cu-rich core at an oxidation potential (see Figure 3f). Most of the magneto-transport measurements were performed by simply contacting a small number of nanowires parallel to each other embedded in the porous matrix. However, measurements on single nanowires were also realized in previous studies [17; 21; 30; 41; 73]. Various experimental approaches have been developed for this purpose. For polymer templates with low pore density, a self-contacting technique [17; 72] has been used successfully for contacting a single wire. For anodic porous alumina supported on Si substrate, nanolithography-based contacting techniques have been developed to allow the electrical connection of one single nanowire in a large assembly of wires [30; 41]. Another approach is based on the use of electron beam lithography to connect a single nanowire after dissolution of the matrix that contains the nanowires [21]. Recently, 3D nanoporous templates were obtained by performing a sequential multi-step exposure of energetic heavy ions, at various angles with respect to the normal of polycarbonate film surface [60; 74]. Then, the latent tracks within the polymer film were chemically etched following the previously reported protocol to obtain membranes with distinct porosities and pores sizes [68]. Hereafter, the as-prepared polymer membranes containing networks of interconnected cylindrical nanopores were designed with pores of well-defined diameters between 40 and 230 nm and with different porosity characteristics (\(P=3\%\) and \(P=20\%\), with \(P\) the void volume fraction of the membrane). Next, the template-assisted electrodeposition method was used for the synthesis of well-defined 3D architecture consisting of crossed nanowire (CNW) and nanotube (CNT) networks [60; 61; 62; 63; 66]. In addition, magnetic and non-magnetic layers were electrochemically stacked to make interconnected multilayered nanowires [64; 65; 67]. Figure 4 illustrates the various 3D nanofiber architectures which have so far been investigated. After electrodeposition, the complete dissolution of the PC template leads to an interconnected metallic self-standing structure, as the one observed for the 40 nm and 230 nm diameter Ni CNW network shown in Figure 4e-g. The CNW network exhibits the replicated complex nanowires branching morphology of the porous template. Figure 4: (**a**) schematics of 3D nanoporous polymer template, (**b**) crossed nanowire and (**c**) crossed nanotube networks, and (**d**) crossed multilayered nanowire network; (**e–h**) SEM images of self-supported interconnected nanowire and nanotube networks; (**e,f**) Ni NW network film with 230 nm diameter; (**g**) Ni NW network film with 40 nm diameter; (**h**) Ni crossed nanotube network with 230 nm diameter. The feasibility of using the same electrochemical method to fabricate large-scale 3D Ni CNT networks from Cu/Ni-core/shell nanocables was recently demonstrated [63]. This process results in Ni CNT networks as the one shown by the SEM micrograph reported in Figure 4h after dissolution of the host PC membrane. In addition, since the geometrical features of the crossed core(Cu)/shell(Ni) nanocables can be carefully modified via the control over the reduction or deposition potential, Ni CNT networks with different wall thickness in the range 10-50 nm were obtained after carrying out the dealloying step of the Cu core [63].