Solution-Phase Synthesis and Magnetic Properties ofSingle-Crystal Iron Germanide Nanostructures.

Iron–germanium(Fe–Ge) is a complex alloy systemthat includes several structurally and compositionally diverse phasesthat exhibit a range of interesting magnetic properties that can changesignificantly when reduced to nanoscale dimensions. Fe–Ge nanostructureshave been synthesized using chemical and physical deposition methodsbut have not previously been accessible as solution-synthesized colloidalmaterials. Here, we show that colloidal Fe–Ge nanostructurescan be synthesized via the hot injection of an oleylamine solutionof Fe(CO)5into a solution containing GeI4,oleylamine, oleic acid, and hexamethyldisilazane. This approach effectivelymerges recent advances in the synthesis of colloidal Ge nanocrystalswith methods routinely used to synthesize metal and alloy nanoparticles.At 260 °C, spherical nanocrystals of Ni2In-type Fe3Ge2form. Heating the solution at 300 °C transformsthe spherical Fe3Ge2nanocrystals into CoGe-typeFeGe nanowires. The Fe3Ge2nanocrystals areferromagnetic with Tc≈ 265 K,whereas the FeGe nanowires are only weakly magnetic. [ABSTRACT FROM AUTHOR]