Chang K. Kim

Formation of periodic magnetic structure by localized amorphization of crystalline Co2MnSi using femtosecond laser

Femtosecond laser-interference induced amorphization (FLIA) was used to form a spatially periodic magnetic structure by selectively amorphizing the surface of bulk Co2MnSi. Regularly spaced alternating lines with a periodicity of 2μm were produced by FLIA. Magnetic force microscopy of the samples clearly revealed one-dimensional periodic magnetic domains resulting from the modulated surface structure which was confirmed by transmission electron microscopy. The periodicity of the modulated structure can be further decreased or the process can be modified to write two-dimensional pattern so that the resulting magnetic structure can be potentially utilized for a permanent magnetic identification.

Fabrication of Ni nanoparticles by selective oxidation of permalloy thin film during imidization of polyamic acid

Ni nanoparticles embedded in a polyimide (PI) matrix were fabricated by selectively oxidizing a layer of Ni(80)Fe(20) metal film sandwiched between two PI precursor layers. Ni nanoparticles, formed in a monolayer between two PI layers, had an average particle size of approximately 5 nm. X-Ray photoelectron spectroscopy confirmed that Fe in the film was preferentially consumed, resulting in the formation of Ni nanoparticles.

Deposition of Sn/SnO x core-shell nanoparticles on phospholipid membrane

Through direct deposition of Sn on a solid-supported phospholipid membrane, a monolayer of self-assembled Sn/SnOx core-shell nanoparticles was fabricated. It was demonstrated that the phase state of the lipid membrane had strong effect on the nanoparticle formation. A flexible phospholipid (l,2-dioleoyl-sn-glycero-3-phosphoethanolamine) membrane in a liquid-crystalline state allowed the metal atoms to penetrate into the membrane and spontaneous formation of nanoparticles whereas a rigid membrane in a gel state (l,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine) retarded nucleation of the nanoparticles on the membrane surface. The proposed method can be extended to other metals and the proper choice of the lipid membrane can be potentially used to alter the resulting particle morphology.