Preparation of monodisperse and highly coercive L10-FePt nanoparticles dispersible in nonpolar organic solvents

A method to prepare monodisperse and highly coercive L1(0)-FePt nanoparticles that are dispersible in nonpolar organic solvents such as toluene, chloroform, and hexane was developed. By vigorously stirring the SiO2-coated L1(0)-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.