Hard Magnetic FePt Nanoparticles by Adsorption-Annealing and Orientation Control

Chemically synthesized FePt nanoparticles are attractive material for magnetic recording media, because of the small size and narrow size distribution. Here we report the fabrication of hard magnetic fct-FePt nanoparticles from chemically synthesized superparamagnetic FePt nanoparticles by annealing following their adsorption onto a zeolite surface. This process enabled the preparation of colloidal fct-FePt nanoparticles with average size of 5.1 nm and size distribution of 8%, respectively. The thus obtained fct-FePt nanoparticles can be oriented using baking in a magnetic field; the resultant coercivities at 300 K are 3.09 kOe and 9.86 kOe in the parallel and perpendicular directions respectively.