| Research Abstract |
The duality nature of the f electrons, i.e. itinerant or localized, is an essential issue of the strongly correlated f electron systems. The purpose of the present project is to investigate the physical properties arising from the duality nature of the 5f electrons in uranium compounds.
We have discovered a new uranium compound U_3Pd_<20>Si_6 and have successfully grown its high-quality single crystals. We have also grown the single crystals of the rare earth compounds R_3(R=La, Pr, Ce, Nd)Pd_<20>Ge_6 whose crystal structure is the same as that of U_3Pd_<20>Si_6, and measured the physical properties and electronic structures of these compounds for comparison.
We have performed a systematic investigation on the transport, magnetic and thermal properties of this compound. Two magnetic transitions at 19K and 2K is found from the resistivity, susceptibility and specific heat measurements. The magnetic moment is found to be as large as 3.3 μ_B and the entropy released up to 19K amounts to Rln3. These results indicate that the 5f electrons of this compound is very likely to be localized. A preliminary neutron experiment also suggest that the crystal field excitation is observable. There are only a few uranium compounds which are metallic and at the same time whose 5f electrons are proved to be localized. The new compound will contribute to improve our understanding of the duality nature of the 5f electrons in the uranium compounds.
We have also studied the physical properties arising from the itinerant or localized nature of the f electrons in other uranium compound like UPd_2Al_3, UNi_2Al_3 and U_2Rh_3Si_5.
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