Fe-Ni-Co Electrodeposited Nanowires Decorated with Au

Abstract

Alloy nanowires containing Fe, Ni and Co are of interest as electrode materials in miniaturized devices due to their ability to align them under a magnetic field. In order to improve their resistivity while retaining their magnetic behavior, Fe-Ni-Co nanowires were electrodeposited and decorated with Au; single nanowires were then further characterized (Fig. 1). The nanowires were deposition under a constant applied potential within a nanoscale alumina template, followed by dissolution of the membrane, release of the nanowires, and subsequent treatment in a gold acid electrolyte. Au clusters formed on the Fe-Ni-Co surface through simultaneous displacement and corrosion reactions. The morphology, composition and structure was examined before and after modification, revealing a change in crystallinity and composition that impacted the nanowire’s electrical and magnetic properties. Transferring a single nanowire to a lithographically prepared two-point probe enabled the electrical and magnetic characterization of the Au decorated nanowire. Averaging results of quadruplicate replicates, a low coverage of discontinuous Au clusters on Fe-Ni-Co nanowires significantly decreased the resistivity, not attributed entirely to the lower resistivity of Au, but as a consequence of changes of the Fe-Ni-Co crystallinity. A high coverage of the Fe-Ni-Co by Au had no further benefit, and even increased the resistivity. Since bulk gold is diamagnetic and decoration of Au onto the Fe-Ni-Co nanowires may compromise the overall magnetic property, the magnetoresistance and electron mobility were determined. Both decreased, as expected, with coverage of Au clusters on the nanowires, suggesting that there may be an optimal cluster density for modifying the Fe-Ni-Co nanowires. Figure 1. Electrodeposited nanowires initially amorphous then decorated with Au showing a change in crystallinity and subsequent characterization with a two-point probe. Figure 1