Chemically L10-ordered face-centered tetragonal (fct) FePt nanocrystals are of great interest because of their large magnetocrystalline anisotropy,[1,2] which makes them excellent candidates for applications in ultrahigh-density recording media and for use in biological separation.[3–5] There have been considerable efforts to organize FePt nanocrystals for such applications by nanocrystal self-assembly[3] and polymer templating.[6] It has been predicted that fct FePt particles as small as 2.8 nm exhibit sufficiently high ferromagnetic stability against superparamagnetism at room temperature.[7] These ultrasmall ferromagnetic particles could be useful for various high-density applications.