New Development of Heavy Electron Systeme including Transuranium Compound

我们生长了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、磁性和超导电性。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的电子态与压力P的关系，在P_c：T_N→_0的临界压力下T_N变为零。实验表明，在P_c=2.35 Gpa时，CeNiGe_3，Ce_2Ni_3Ge_5，CeNiGe_3，CeNiGe_3，Ce_3Ge_5，CeNiGe_3，Ce_2Ni_3Ge_5的压力感生超导电性在P_c：T_N→_0时变为零CeIrSi3和ULR。观察到了有趣的超导性质，特别是在晶体结构中没有反转对称性的CeIrSi3和UIr中。例如，CeIrSi3的反铁磁态在2 Gpa左右变为超导。令人惊讶的是，当磁场向四方[001]方向施加时，在2.6 Gpa处发现了约40T的大的上临界场。(3)我们在NPPd_5Al_2中也发现了超导电性，其转变温度T_sc=5K。此外，我们还成功地探测到了NpGe_3和PuIn_3的超铀化合物中的dHvA跃迁，表明这些化合物中的5f电子是巡回的。SoC。日本。以及《在CeRhIn_5中临界压力下费米表面的剧烈变化：压力下的dHvA研究》，H.Shishido，R.settai，H.Harima和Y.Onuki：J.Phys.Soc.Jpn.74(2005)1103-1106。入选“第十三届J.Phys.SoC.Jpn.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 ".