Synthesis of monodisperse FePt nanoparticles by pulsed laser ablation

The continuous drive to further miniaturization is one of the basic research and development goals in industry producing data processing and storage devices, for reasons of economy, performance and energy minimisation. Modern magnetic hard drives have storage densities of hundreds of GBits / in² , but future storage devices are required to reach values of over 1 TBits/ in². Ideally, a single domain magnetic nanoparticle could represent a single data bit. A main issue for reaching this is the thermal stability of magnetisation if the superparamagnetic limit is reached. The most promising material is the bimetallic alloy FePt which offers large magnetic anisotropy due the presence of the ordered face centered tetragonal phase. In the frame of this objective a synthesis process by means of the physical approach of evaporation and recondensation in the gas phase was developed and optimized. Thereby ns-Pulsed Laser Ablation was applied on a FePt rod inside a vacuum-tight facility. The FePt nanoparticles were size selected by means of a Differential Mobility Analyzer and annealed in order to obtain desired spherical shape and magnetic properties.