Synthesis of Magnetic Ultrafine Particles from a Ternary Gaseous Mixture Involving Cobalt Tricarbonyl Nitrosyl

Abstract

From a ternary gaseous mixture of cobalt tricarbonyl nitrosyl (Co(CO)₃NO), tetraethylgermane (TEG), and propenyltrimethylsilane (allyltrimethylsilane) (ATMeSi), magnetic ultrafine particles were produced under irradiation with intense Nd:YAG laser light. From FT-IR spectra, chemical structure of the ultrafine particles was investigated. The spectrum of the magnetic particles was essentially the same to the one of the ultrafine particles produced from a binary gaseous mixture of Co(CO)₃NO and ATMeSi, suggest- ing strongly that TEG molecules did not contribute significantly to particle formation process. On the other hand, in the gaseous phase, depletion rate of TEG molecules was accelerated by 800 times due to the presence of Co(CO)₃NO molecules, showing that TEG molecules interacted efficiently with Co(CO)₃NO molecules to produce some volatile chemical species in the gas phase under laser light irradiation. Magnetization of the ultrafine particles was measured using a SQUID magnetometer. Magnetic susceptibility of the ultrafine particles was evaluated to be ∼1×10^-2 emu/g, suggesting that the deposited ultrafine particles were mainly composed of ferromagnetic species. The morphology of the coagulated particles was studied by taking HRTEM images. The ultrafine particles were composed of several kinds of particles which involved both the polycrystalline phase and amorphous phase. Crystalline phase was mainly composed of Co atoms, and may be responsible for ferromagnetic properties of the particles.