Magnetic properties of Au1-xFex nanowires

We have investigated the magnetic properties of Au_1-xFe _x (x=0.03,0.15) nanowire arrays by performing magnetization and magnetoresistance (MR) measurements between 4.2 and 300 K. The Au _1-xFe_x 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 Au_0.85 Fe_0.15 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 Au _0.97Fe_0.13 wires and 14% for the Au_0.85Fe_0.15 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 Fe clusters in Au_0.97Fe_0.03 wires consist of 1-6 Fe atoms with K≈80 J/cm³, while Au_0.85Fe_0.15 wires contain a much broader cluster size range with Fe clusters consisting of 1-40 Fe atoms with K≈60 J/cm³