Magneto-Transport in Flexible 3D Networks Made of Interconnected Magnetic Nanowires and Nanotubes

Abstract

Electrochemical deposition of interconnected nanowires and nanotubes made of ferromagnetic metals into track-etched polycarbonate templates with crossed nanochannels has been revealed suitable for the fabrication of mechanically stable three-dimensional magnetic nanostructures with large surface area. These 3D networks embedded into flexible polymer membranes are also planar and lightweight. This fabrication technique allows for the control of the geometric characteristics and material composition of interconnected magnetic nanowire or nanotube networks, which can be used to fine-tune their magnetic and magneto-transport properties. The magnetostatic contribution to the magnetic anisotropy of crossed nanowire networks can be easily controlled using the diameter, packing density, or angle distribution characteristics. Furthermore, the fabrication of Co and Co-rich NiCo alloy crossed nanowires with textured hcp phases leads to an additional significant magnetocrystalline contribution to the magnetic anisotropy that can either compete or add to the magnetostatic contribution. The fabrication of an interconnected nanotube network has also been demonstrated, where the hollow core and the control over the tube wall thickness add another degree of freedom to control the magnetic properties and magnetization reversal mechanisms. Finally, three-dimensional networks made of interconnected multilayered nanowire with a succession of ferromagnetic and non-magnetic layers have been successfully fabricated, leading to giant magnetoresistance responses measured in the current-perpendicular-to-plane configuration. These interconnected nanowire networks have high potential as integrated, reliable, and stable magnetic field sensors; magnetic devices for memory and logic operations; or neuromorphic computing.

Control of the asymmetric growth of nanowire arrays with gradient profiles

“…The method also complements currently known processes for modulating the shape and micrometer-scale geometric features of NW template-assisted electrochemical growth in three dimensions. Overall, this method can be adapted for many of the NW growth variations based on the usual continuous electrode approach, like diameter modulation in anodic aluminum oxide membranes, 56 multilayered NWs, 57 and interconnected NWs, 58 to produce novel 3D modulated NW arrays.…”

Magnetically Activated Flexible Thermoelectric Switches Based on Interconnected Nanowire Networks

“…Co x Ni 1−x CNWs were deposited by direct electrodeposition at constant potential of −1 V from home-made electrolyte solutions containing the Ni 2 + and Co 2 + cations, as described elsewhere. [29,35,36] The alloying composition was controlled by modifying the Co 2 + cation concentration from 5 to 170 mM within the electrolyte solutions containing 1 M of Ni 2 + , which allowed for a Co content x from ≈3% up to ≈53%. For such alloy compositions, it has been shown from XRD measurements that Co x Ni 1−x CNWs exhibited an FCC structure.…”

“…[21,23] These giant magneto-transport phenomena are displayed in the currentperpendicular-to-plane (CPP) configuration that are easily measurable along the macroscopic in-plane dimensions of the network films. [21,22,24,29] The other branch, consisting of homogeneous NWs, has Seebeck coefficients between −30 μV K −1 (pure Co) and −20 μV K −1 (pure Ni) and shows very weak magneto-Seebeck effects. [24] Therefore, by appropriately selecting the magnetic materials and multilayers that make up the two legs of the thermocouple, we achieve high variability in the output power of the nanowire-based thermoelectric generator when the system is exposed to an external magnetic field.…”

Giant Magnetoresistance and Magneto-Thermopower in 3D Interconnected NixFe1−x/Cu Multilayered Nanowire Networks

“…Their robust and self-standing structure with a high degree of NW interconnectivity and high surface over volume ratio makes them attractive nano-device components for a large range of applications. For instance, they have potentials in energy harvesting and storage systems [ 5 , 6 , 7 , 8 ], biosensors and bio-analytical devices [ 9 , 10 , 11 ], magnetic and spintronic devices [ 12 , 13 , 14 ], and thermoelectric and spin caloritronic devices [ 15 , 16 , 17 , 18 ]. Direct electrodeposition into polymer template films containing networks of crossed nano-channels has proved to be a suitable technique to grow a wide variety of 3D NW networks with controllable morphologies, geometrical parameters, and sizes [ 1 , 2 , 12 ].…”

“…In addition, the polymer-NWs composite is flexible and lightweight, which are important advantages of this structure [ 15 , 16 ]. The composite film can be twisted or can have a different shape without damaging the high electrical and thermal interconnectivity in the large amount crossing points of the macroscopic structure [ 14 , 18 ].…”