プラスチック中に分散したコバルト・ナノ粒子の磁気および磁気光学特性  [in Japanese] Magnetic and Magneto-optical Properties of Nano-size Cobalt Particles Dispersed in a Plastic  [in Japanese]

Because of the importance of understanding the physical properties of materials in microscopic systems, there has been a growing interest in ultra-fine particles. To obtain nano-size ferromagnets, we used nano-size Co particles prepared by decomposing dicobalt octacarbonyl [Co_2(CO)_8: DOOC] in a polymethyl-methacrylate (PMMA) solution in toluene. The magnetic, magneto-optical, and optical properties of these samples were measured for Co particles ranging from 3.3 nm to 15.9 nm in mean diameter, which were prepared by reducing the solvent/solution ratio. The Faraday spectra of these samples retained a similar wavelength dependence regardless of the size of the Co particles, but the Faraday rotation per magnetic moment increased with decreasing Co particle size. The peak of the optical extinction spectra shifted toward the higher-energy side (blue shift), and a periodic change in the derivative of the extinction spectra appeared for Co particles smaller than 7.8 nm in mean diameter, this may be due to the size effect of the surface plasmon.