Anomalous metallic-like transport of Co-Pd ferromagnetic nanoparticles cross-linked with π-conjugated molecules having a rotational degree of freedom

Yoshikazu Ito, Kazuyuki Takai, Akira Miyazaki, Vajiravelu Sivamurugan, Manabu Kiguchi, Yoshihiro Ogawa, Naotake Nakamura, Suresh Valiyaveettil, Tomofumi Tada, Satoshi Watanabe, Toshiaki Enoki

    Research output: Contribution to journalArticlepeer-review

    3 Citations (Scopus)

    Abstract

    We investigated the electron transport in Co-Pd ferromagnetic nanoparticles (Co 16%) cross-linked with oligo(phenyleneethynylene)diethanethiolate, which consists of three rotary phenylene moieties bridged by two acetylene groups, or icosane-1,20-dithiol, which consists of one alkane chain. Although the nanoparticles cross-linked with the alkane dithiols (the latter) have extremely high electrical resistance in electron transport, the resistance of the nanoparticles cross-linked with the conjugated molecules (the former) demonstrates a linear temperature dependence from room temperature to ca. 20 K; below that temperature, it has a weak temperature-dependent residual contribution with a resistance minimum around 7 K. Computational simulations suggest that the apparent metallic-like temperature dependence at high temperatures can be explained in terms of the rotational degree of freedom of the linker molecule. The rotational motion of the constituent phenylene groups, which hinders π-conjugation along the linker molecule, becomes less excited as the temperature is lowered. The successive development of a ballistic transport path through the π-conjugated linker molecule with decreasing temperature yields the metallic-like temperature dependence observed for the bridged nanoparticles. The low-temperature resistance behaviour with a minimum is a consequence of carrier scattering by the localized Co spins of Co-Pd nanoparticles randomly ordered in a ferromagnetic state that develops below the temperature of the resistance minimum.

    Original languageEnglish
    Pages (from-to)288-296
    Number of pages9
    JournalPhysical Chemistry Chemical Physics
    Volume16
    Issue number1
    DOIs
    Publication statusPublished - 2014 Jan 7

    ASJC Scopus subject areas

    • Physics and Astronomy(all)
    • Physical and Theoretical Chemistry

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