Chemical synthesis and magnetic properties of well-coupled FePt/Fe compositenanotubes

Abstract

A simple two-step hydrogen reduction method was used to synthesize FePt/Fe composite nanotubes. As thefirst step, L10 FePt nanotubes were prepared by heating a porous alumina template loaded with analcohol solution of a Fe chloride and Pt chloride mixture in flowing hydrogen at670 °C. Then, FePt/Fe composite nanotubes were obtained by reducing the alcohol solution of theFe chloride within the formed FePt nanotubes at a lower temperature, namely470 °C.Through changing the concentrations of initial alcohol solutions, the FePt:Fe atomic ratios of thecomposite nanotubes were easily adjusted and the magnetic properties were tuned accordingly. For(FePt)100−x/Fex compositenanotubes with x ranging between 0 and 26 at.%, the hard and soft phases were well coupled andthe coercivity was tunable over a large range (1.27–2.73 T). Furthermore, themarked interdiffusion between Fe and FePt, which usually exists in FePt-basedcomposites fabricated by using conventional methods, was not observed in the formedcomposite nanotubes. This indicates the two-step hydrogen reduction method to be apromising route for synthesizing nanocomposites which are difficult to fabricate byusing conventional methods due to the interdiffusion between different phases.