Browsing by Author "Watanabe, Y"

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    Clustering of charged colloidal particles in the microgravity environment of space
    (Springer Nature, 2023-04-29) Miki,.H.; Ishigami, T; Yamanaka, J; Okuzono, T; Toyotama, A; Mata, JP; Komazawa, H; Takeda, Y; Minami, M; Fujita, M; Doi, M; Higuchi, T; Takase, H; Adachi, S; Sakashita, T; Shimaoka, T; Nagai, M; Watanabe, Y; Fukuyama, S
    We conducted a charge–charge clustering experiment of positively and negatively charged colloidal particles in aqueous media under a microgravity environment at the International Space Station. A special setup was used to mix the colloid particles in microgravity and then these structures were immobilized in gel cured using ultraviolet (UV) light. The samples returned to the ground were observed by optical microscopy. The space sample of polystyrene particles with a specific gravity ρ (=1.05) close to the medium had an average association number of ~50% larger than the ground control and better structural symmetry. The effect of electrostatic interactions on the clustering was also confirmed for titania particles (ρ ~ 3), whose association structures were only possible in the microgravity environment without any sedimentation they generally suffer on the ground. This study suggests that even slight sedimentation and convection on the ground significantly affect the structure formation of colloids. Knowledge from this study will help us to develop a model which will be used to design photonic materials and better drugs. © 2023 The Authors, Open Access under a Creative Commons Attribution 4.0 International License. Published in cooperation with the Biodesign Institute at Arizona State University, with the support of NASA.
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    Stripelike magnetism in a mixed-valence insulating state of the Fe-based ladder compound CsFe2Se3
    (American Physical Society, 2012-06-28) Du, F; Ohgushi, K; Nambu, Y; Kawakami, T; Avdeev, M; Hirata, Y; Watanabe, Y; Sato, TJ; Ueda, Y
    Structural and electronic properties of the Fe-based spin-ladder compound CsFe2Se3 was investigated by means of resistivity, susceptibility, specific heat, Mossbauer, and neutron diffraction measurements. Despite the single-site nature in a mixed-valence state, the ground state is a magnetic insulator characterized by a charge gap similar to 0.34 eV and an antiferromagnetic transition temperature 175 K. The magnetic structure was stripelike, with magnetic moments of 1.77(6)mu(B) coupled ferromagnetically (antiferromagnetically) along the rung (leg) direction. Both the insulating behavior and stripelike ordering can be understood by assuming extra carriers delocalized on the rung. Our findings reveal that CsFe2Se3 is an appealing compound with the stripelike magnetic structure in an insulating state among Fe-based compounds, and provide significant supplemental insight into the magnetism of Fe-based superconductors. © 2012, American Physical Society.