Uhg3: A Heavy-Fermion Antiferromagnet Similar To U2zn17 And Ucd11

Heavy-fermion physics deals with the ground state formation and interactions in f-electron materials where the electron effective masses are extremely large, more than 100 times the rest mass of an electron. The details of how the f electrons correlate at low temperature to become so massive lacks a coherent theory, partially because so few materials display this "heavy" behavior and thus global trends remain unclear. UHg3 is now found experimentally to be a heavy-fermion antiferromagnet-just as are all the other UxMy compounds with the metal M being in column IIB (filled d-electron shells) in the periodic table (Zn/Cd/Hg) and the spacing between uranium ions d(U-U) being greater than the Hill limit of 3.5 angstrom. This result, that-independent of the structure of these UxMy, M = Zn/Cd/Hg, compounds and independent of the value of their d(U-U) (ranging from 4.39 to 6.56 angstrom)-all exhibit heavy-fermion antiferromagnetism, is a clear narrowing of the parameters important for understanding the formation of this ground state. The sequence of antiferromagnetic transition temperatures T-N of 9.7, 5.0, and 2.6 K for UxMy as the metal M varies down column IIB (Zn/Cd/Hg) indicates an interesting regularity for the antiferromagnetic coupling strength.