Heavy-Fermion and Semiconducting Properties of the Ternary Uranium Compounds U_3T_3Sn_4 and U_3T_3Sb_4(T=Ni,Cu,Pd,Pt and Au)

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We present results of magnetic, transport and calorimetruc measurements onU.T,X. with T=Ni, Cu, Pd, Pt and Au and X=Sn and Sb. A heavy-fermionbehavior manifests itself in U.T.Sn., where the electronic specific-heat coefficient in-creases from 90mJ/K'rno1U for T=Ni and PI to about 30OmJ/K'mo1U forT=Cu and Au. We ascribe the mass enhancement to the dehybridization of 5f elecirons with the d electrons derived from the T atom. On the other hand, U,T.Sb. withT=Ni, Pd and PI shows a serniconducting behavior with a band gap of about 0.2 eV,whereas U.Cu.Sb. is a metallic ferromagnet with T.=9I K. In these antimonides, 5felectrons are localized because of the weak hybridization with the 5p electrons fromthe Sb atom. These results indicate total the number of 5p electrons in the presentsystem determines whether the system shows heavy-fermion or semiconductingbehavior.
社団法人日本物理学会の論文
1990-12-15