  A method to prepare monodisperse and highly coercive L10-FePt nanoparticles
which are dispersible in nonpolar organic solvents such as toluene, chloroform,
and hexane was developed. By vigorously stirring the SiO2-coated L10-FePt
nanoparticles synthesized by the SiO2-nanoreactor method (Appl. Phys. Lett.
2005, 87, 032503) in a mixture of an aqueous NaOH solution, chloroform, and
hexadecyltrimethlyammonium bromide, the SiO2 coating was dissolved off and bare
FePt nanoparticles could be extracted to the chloroform phase without degrading
their magnetic properties. These particles showed a tendency to form a close
packed lattice on slow drying of the chloroform-based solution. The present
success may promote the practical application to ultra-high density magnetic
recording and also may open the door to providing these particles with new
physical and/or chemical functions.
