Assembly and patterning of ferromagnetic nanoparticles from solution: A novel low-temperature liquid-phase annealing approach

Ferromagnetic L10-phase FePtAu nanoparticles (5–6 nm) were prepared using a low-temperature, liquid phase annealing approach. The chemically ordered, ferromagnetic L10-phase onset occurs for annealing temperatures as low as 150 °C. Large uniaxial magnetic anisotropy (Ku ∼ 107 erg/cm3) and a large long-range ordering parameter have been obtained. Significantly, the low-temperature liquid-phase annealing preserves the organic functionalization groups of the nanoparticles. Hence, these nanoparticles are flexible for further assembly and patterning. In addition, we present the assembly of FePt nanoparticles on ferromagnetic substrates with a thin alumina capping layer. This enables us to investigate spin dependent transport through the FePt nanoparticles by scanning tunneling microscopy.