Magnetically superior and easy to handle L10-FePt nanocrystals -: art. no. 032503

We report synthesis of monodisperse L1(0)-FePt nanocrystals that are not only superior in magnetism but also easy to handle through being dispersible in solvents. Thanks to a thick SiO2 coating, the thermal treatment needed to form the L1(0) structure can be done even at 900 degrees C without inducing coalescence and coarsening. The protecting shell was thereafter removed in a specific way that enabled us to recover the L1(0)-FePt nanocrystals in a water dispersion. The SiO2-coated nanocrystals show a high coercivity of 18.5 kOe at room temperature in spite of their core size of only 6.5 nm in diameter, and the hysteresis loop of the water-dispersed nanocrystals, which were frozen under an external field, was almost rectangular indicating that their magnetic and structural orientation could be attained. (c) 2005 American Institute of Physics.