Abstract
Anodized aluminum oxide (AAO) films, which have numerous nanochannels ca. 75 nm in diameter, D and ca. 70 µm in length, L (ca. 933 in aspect ratio, L/D), were used as a template material for growing Co/Cu multilayered nanowire arrays. The multilayered nanowires with alternating Cu layer and Co layers were synthesized by using an electrochemical pulsed-potential deposition technique. The thickness of the Cu layer was adjusted from ca. 2 to 4 nm while that of the Co layer was regulated from ca. 13 to 51 nm by controlling the pulsed potential parameters. To get a Co/Cu multilayered nanowire in an electrochemical in-situ contact with a sputter-deposited Au thin layer, the pulsed potential deposition was continued up to ca. 5000 cycles until the nanowire reached out toward the surface of AAO template. Current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) effect reached up to ca. 23.5% at room temperature in Co/Cu multilayered nanowires with ca. 3500 Co/Cu bilayers (Cu: 1.4 nm and Co: 18.8 nm). When decreasing the thickness of Co layer, the CPP-GMR value increased due to the Valet–Fert model in the long spin diffusion limit.
Highlights
IntroductionDue to a uniaxial shape anisotropy and a large surface area, metallic nanowires with an extremely large aspect ratio have a variety of potential applications to novel functional devices [1,2,3,4]
Due to a uniaxial shape anisotropy and a large surface area, metallic nanowires with an extremely large aspect ratio have a variety of potential applications to novel functional devices [1,2,3,4].ferromagnetic metal nanowires are expected to be able to apply for a magnetic field sensor with anisotropic magnetoresistance response [5,6] or giant magnetoresistance response [7,8].Metallic nanowires can be synthesized by a metal-catalyzed vapor-phase method [9] or a wet chemical etching method [10]
Co/Cu bilayers (Cu) multilayered nanowires were synthesized by using a pulsed-potential deposition technique from an aqueous solution
Summary
Due to a uniaxial shape anisotropy and a large surface area, metallic nanowires with an extremely large aspect ratio have a variety of potential applications to novel functional devices [1,2,3,4]. Metallic nanowires can be synthesized by a metal-catalyzed vapor-phase method [9] or a wet chemical etching method [10]. Some researchers have reported that the nanowires can be fabricated by the electrochemical growth of metallic crystals from an aqueous solution into nanochannel template materials [11,12,13]. The electrodeposition technique into numerous nanochannels has a large merit rather than the others with respect to the productivity of numerous nanowires with straight shape. Polymer-based nanochannel films [14,15] and aluminum-oxide-based nanochannel films [16,17,18]
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