Anisotropic Magnetoresistance of Ni-Co-Fe Alloy Nanowires Electrodeposited into Anodized Aluminium Oxide Membrane Thin Films

Abstract

To synthesize a novel anisotropic magnetoresistance (AMR) sensor, Ni-Co, Ni-Fe, Co-Ni and Co-Fe alloy nanowires were electrodeposited into nano-channels of anodized aluminium oxide films with the thickness ranging from 20 μm to 200 μm. The growth rate of the nanowires was around 200 nm/sec at the cathode potential of -1.2 V vs. Ag/AgCl. The aspect ratio of the nanowires reached up to ca. 3,000 to 1 and the cylindrical shape was precisely transferred from the nano-channels to the nanowires. Magnetic hysteresis loops of Ni-Co, Ni-Fe, Co-Ni and Co-Fe alloy nanowires with the diameter of 60 nm showed typical perpendicular magnetization behaviour due to the uni-axial shape anisotropy and the coercive force reached up to 1 kOe. 3.2% of AMR was observed in Co-1.5%Ni alloy nanowires with the aspect ratio of 1,000.