Netsu Sokutei
Online ISSN : 1884-1899
Print ISSN : 0386-2615
ISSN-L : 0386-2615
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Review
  • Heat Dissipation Properties and Biomedical Application of Magnetic Nanoparticles
    Yuko Ichiyanagi
    2025 Volume 52 Issue 2 Pages 53-58
    Published: April 25, 2025
    Released on J-STAGE: June 12, 2025
    DOIhttps://doi.org/10.11311/jscta.52.2_53
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    Magnetic nanoparticles have drawn attention recently due to their interesting nanoscopic features and otential applications. Various kinds of ferrite nanoparticles with diameters between 3 and 34 nm encapsulated by amorphous SiO2 were functionalized and examined for biomedical applications. From dc and ac magnetic susceptibility measurements, it was found that these particles followed the Néel relaxation system. Ferrite nanoparticles such as Co-Zn ferrite (Co0.8Zn0.2Fe2O4) and Mn-Zn ferrite nanoparticles were prepared and the increase in temperature in the ac field was estimated for hyperthermia treatment. In vitro experiments using cultured human breast cancer cells were carried out, and a significant hyperthermia effect was observed. As one of the diagnostic methods, magnetic resonance (MR) measurements were performed for magnetic nanoparticles, and these materials were also evaluated as potential contrast media for MR imaging. Theranostics, which combines treatment and diagnosis, is expected to be developed.
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  • Quasiparticle Excitation Spectra in Organic Superconductors Probed from Thermodynamic Quantities
    Shusaku Imajo
    2025 Volume 52 Issue 2 Pages 59-64
    Published: April 25, 2025
    Released on J-STAGE: June 12, 2025
    DOIhttps://doi.org/10.11311/jscta.52.2_59
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    Superconductivity is one of the most fascinating phase transition phenomena, offering deep insights into fundamental physics. In organic charge-transfer complexes, superconductivity is believed to arise from unconventional mechanisms beyond the conventional BCS theory. To explore the mechanisms underpinning unconventional superconductivity in organics, we investigated the quasiparticle spectra in the superconducting state through thermodynamic measurements. For the κ-type organic system, comprehensive heat capacity measurements revealed detailed quasiparticle excitation spectra. These results demonstrated that the superconducting state exhibits either dx2-y2-wave or dxy-wave symmetry, depending on the dimer lattice structure. This finding suggests that the superconductivity in κ-type systems originates from two types of antiferromagnetic spin fluctuations. In contrast, the β″-type organic system, which lacks antiferromagnetic spin fluctuations, was found to exhibit a quasiparticle excitation spectrum different from that of the κ-type system. In this case, charge fluctuations driven by intersite Coulomb repulsions were identified as the origin of the primary mechanism for Cooper pairing. These results highlight that the determination of quasiparticle excitation spectra using thermodynamic quantities is a powerful approach to uncovering the detailed origins of superconductivity in organic systems.
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  • Development of Plastic/Ferroelectric Crystals
    Jun Harada
    2025 Volume 52 Issue 2 Pages 65-71
    Published: April 25, 2025
    Released on J-STAGE: June 12, 2025
    DOIhttps://doi.org/10.11311/jscta.52.2_65
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    Plastic crystals are a class of compounds composed of molecules with globular structures. Plastic crystals exhibit several unique features arising from isotropic rotator motion of their constituent molecules. We have discovered that certain plastic crystals based on ionic molecules undergo phase transitions to ferroelectric phases upon cooling. These crystals, i.e., plastic/ferroelectric crystals display several unique features that differ from conventional molecular ferroelectric crystals. In particular, the materials have achieved ferroelectric performance for the first time as bulk polycrystals composed of small molecules. In this article, we outline the development and distinctive features of plastic/ferroelectric crystals, focusing on their ferroelectricity and related properties in bulk polycrystalline forms.
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