New Development of Heavy Electron Systeme including Transuranium Compound

我们培育了50种稀土化合物和20种铀和超铀化合物，并研究了这些化合物的费米表面性质、磁性和超导性。实验结果如下：(1)用de Haas-van-Alphen （dHvA）实验研究了反铁磁体CeRhIn_5和CeIn_5的电子态随压力P的变化规律，其中Ne'el温度T_N在临界压力P_c下变为零：T_N→0 at P→P_c。我们通过实验证明，在P_c = 2.35GPa时，4f局域电子态转变为4f流动电子态，揭示了一阶相变。(2)我们发现了CeNiGe_3、Ce_2Ni_3Ge_5、CeIrSi_3和Ulr的压力诱导超导性。在CeIrSi_3和UIr中观察到有趣的超导性质，特别是在晶体结构中没有反转对称性。例如，CeIrSi_3的反铁磁态在2gpa左右变成超导态。令人惊讶的是，当磁场作用于四方方向[001]时，在2.6 GPa处发现了一个大的上临界场，约为40T。CeIrSi_3中H//[001]有可能实现自旋三重态超导。(3)在过渡温度T_sc = 5K时，我们还发现了NpPd_5Al_2的超导性。此外，我们还成功地检测到了NpGe_3和PuIn_3超铀化合物中的dHvA振荡，这表明这些化合物中的5f电子是流动的。我们在J. Phys上发表了七篇论文。Soc。日本。《临界压力下fermissurface在CeRhIn_5中的急剧变化：压力下的dHvA研究》，H. Shishido， R. Settai， H. Harima和Y. Onuki:J。理论物理。Soc。《物理学报》第74期（2005）1103-1106。Soc。日本。论文奖”。

We grew fifty kinds of rare earth compounds and twenty kinds of uranium and transuranium compounds and studied Fermi surface properties, magnetism and superconductivity for these compounds. Experimental results are summarized as follows :(1) The electronic state of antiferromagnets CeRhIn_5 and CeIn_5 was studied by the de Haas-van-Alphen (dHvA) experiment as a function of pressure P, where the Ne'el temperature T_N becomes zero at the critical pressure P_c: T_N → 0 at P → P_c. We clarified experimentally that the 4f - localized electronic state is changed into the 4f - itinerant one at P_c = 2.35GPa, revealing the first-order phase transition.(2) We discovered pressure-induced superconductivity for CeNiGe_3, Ce_2Ni_3Ge_5, CeIrSi_3 and Ulr. Interesting superconducting properties are observed especial in CeIrSi_3 and UIr without inversion symmetry in the crystal structure. For example, an antiferromagneitic states of CeIrSi_3 becomes superconductive around 2 GPa. Surprisingly, a large upper critical field of about 40T is found at 2.6 GPa when the magnetic field is applied to the tetragonal [001] direction. There is a possibility that spin-triplet superconductivity is realized for H//[001] in CeIrSi_3.(3) We also discovered superconductivity in NpPd_5Al_2 with the transition temperature T_sc = 5K Moreover, we succeeded in detecting the dHvA escillations in transuranium compounds of NpGe_3 and PuIn_3, indicating that 5f electrons in these compounds are itinerant.Our seven papers published in J. Phys. Soc. Jpn. were selected as Editor's Choice, and "A Drastic Change of the FermiSurface at a Critical Pressure in CeRhIn_5: dHvA Study under Pressure, H. Shishido, R. Settai, H. Harima and Y. Onuki:J. Phys. Soc. Jpn. 74 (2005) 1103-1106." was selected as" 13th J. Phys. Soc. Jpn. Paper Award ".