Fabrication of FePt nanoparticles for self-organized magnetic array

Abstract

A self-organized array of magnetic nanoparticles can be potentially used to increase the storage density in magnetic recording. One challenge in this approach is to obtain long-range order assemblies of the nanoparticles. One method to solve this problem is to pattern a substrate having circumferential patterns, whose dimensions are within the coherent length of the self-organized array. By patterning the disk into topographically confined circumferential patterns with such dimensions, thermally stable magnetic nanoparticles may be used to fabricate magnetic recording disks. The circumferential patterns in this case are formed on the disk substrate with dimensions of 100–500 nm and depths of 5–20 nm, prepared by electron beam lithography and reactive ion etching techniques. The monodispersed FePt nanoparticles were synthesized by thermal decomposition of iron pentacarbonyl and reduction of platinum salt simultaneously in the presence of surfactant molecules, achieving a size distribution of 3.15±0.20 nm. Our initial experimental results showed that the monodispersed FePt nanoparticles were successfully deposited into the circumferential patterns and they self-organized into a superlattice. The self-assembly of the FePt nanoparticles in the circumferential pattern strongly relied on the line edge roughness (LER) of the circumferential pattern. This suggests that we need to fabricate the circumferential pattern with LER at the length scales of approximate an individual nanoparticle size 3–4 nm in order to improve the assembly quality further. This is another challenge for today’s advanced lithography and etching processes.