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| 21世紀COEセミナー（第２班） |
| 日時 |
平成１６年（２００４年）９月２１日（火）１７：００〜１８：００ |
| 場所 |
コミュニケーションスペース |
| 講師 |
Dr. GRIVEAU Jean-Christoph
(Institute for Transuranium Elements Karlsruhe, Germany) |
| 題目 |
Magnetic Properties of Transuranium Compounds |
| 概要 |
Due to their high radio toxicity and self heating effect, transport properties of transuraniums compounds (Np, Pu, Am, Cm) have been poorly known especially at low temperature (T < 1 K). Pressure studies have been achieved mainly on the crystallographic structure to observe localization-delocalisation of the 5f electrons. We developed recently high pressure resistivity facilities for measurement down to 300 mK and up to 30 GPa. Np, Pu and Am-115 systems compounds have been studied. The dramatic change of superconducting state developing in Am metal at temperature lower than 2 K has set a new challenge to overcome the technical difficulties imposed by the manipulation of these of materials (radio toxicity and heating power of 6.3 mW/g for 243Am). Here we report the main technical advances for the studies of transuranium compounds. We present the Am Tc(p) diagram under 1 K and critical field Hc with pressure assuming a possible change of superconductivity from type I to type II. Pressure results on the recent discovered plutonium based superconductors PuCoGa5 [4] and PuRhGa5 indicate a surprising important robustness vs. mechanical constraints reinforcing the d-wave superconductivity scenario as NQR results stress it. But their Non Fermi Liquid (r~T1.34) is still observed up to pressure close to 20 GPa. Their Neptunium counterparts present a clear magnetism (AFM) reinforced under pressure in the case of NpCoGa5. Finally, recent study of other AnCoGa5 indicate a non magnetic ground state (An=U, Am).
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