Abstract
The versatility of the template-assisted electrodeposition technique to fabricate complex three-dimensional networks made of interconnected nanowires allows one to easily stack ferromagnetic and non-magnetic metallic layers along the nanowire axis. This leads to the fabrication of unique multilayered nanowire network films showing giant magnetoresistance effect in the current-perpendicular-to-plane configuration that can be reliably measured along the macroscopic in-plane direction of the films. Moreover, the system also enables reliable measurements of the analogous magneto-thermoelectric properties of the multilayered nanowire networks. Here, three-dimensional interconnected NiFe/Cu multilayered nanowire networks (with ) are fabricated and characterized, leading to large magnetoresistance and magneto-thermopower ratios up to 17% and −25% in NiFe/Cu, respectively. A strong contrast is observed between the amplitudes of magnetoresistance and magneto-thermoelectric effects depending on the Ni content of the NiFe alloys. In particular, for the highest Ni concentrations, a strong increase in the magneto-thermoelectric effect is observed, more than a factor of 7 larger than the magnetoresistive effect for NiFe/Cu multilayers. This sharp increase is mainly due to an increase in the spin-dependent Seebeck coefficient from −7 µV/K for the NiFe/Cu and NiFe/Cu nanowire arrays to −21 µV/K for the NiFe/Cu nanowire array. The enhancement of the magneto-thermoelectric effect for multilayered nanowire networks based on dilute Ni alloys is promising for obtaining a flexible magnetic switch for thermoelectric generation for potential applications in heat management or logic devices using thermal energy.
Highlights
Three-dimensional (3D) networks made of interconnected high-aspect ratio nanowires (NWs) are unique macroscopic nano-architectures that have raised increasing interest over the last decade [1,2,3,4]
A Cr (3 nm)/Au (400 nm) cathode is sputtered using an e-beam evaporator on one surface of the template from which the multilayered NWs are grown from single home-made electrolyte solution using a pulsed electrodeposition technique at room temperature (RT) in the potentiostatic mode using a Ag/AgCl reference electrode and a Pt counter electrode following the procedure described in [20]
This is in contrast to the measurements previously performed on the 3D NiCo/Cu and Co/Cu NW networks, where the amplitudes of the MR and MTP effects are similar at RT [15,16]
Summary
Three-dimensional (3D) networks made of interconnected high-aspect ratio nanowires (NWs) are unique macroscopic nano-architectures that have raised increasing interest over the last decade [1,2,3,4]. 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. 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]
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