Magnetic properties of Au1-xFex nanowires

We have investigated the magnetic properties of Au1-xFex (x = 0.03, 0.15) nanowire arrays by performing magnetization and magnetoresistance (MR) measurements between 4.2 and 300 K. The Au1-xFex nanowires range from 50-120 nm in width, and are prepared by oblique coevaporation of Au and Fe onto V-groove patterned InP substrates. The magnetization of as-prepared Au0.83Fe0.15 wires shows a zero-field/field-cooled irreversibility, which is typical for granular magnetic materials. The width of the zero-field-cooled maximum indicates a broad distribution of Fe cluster sizes. At 4.2 K the MR ratio has a maximum of 5% for the Au0.97Fe0.13 wires and 14% for the Au0.85Fe0.15 wires. By using a simple superparamagnetic model, the MR can provide quantitative information on the size range of the Fe clusters and their average effective anisotropy constant K. We find that the re clusters in Au0.97Fe0.13 wires consist of 14% Fe atoms with K approximate to 80 J/cm(3), while Au0.85Fe0.15 wires contain a much broader cluster size range with Fe clusters consisting of 1-40 Fe atoms with K approximate to 60 J/cm(3).