New heavy-fermion compounds An(4)PdGa(12) (An = U, Np, Pu)

摘要

An(4)PdGa(12) (An = U, Np and Pu) are new heavy-fermion materials that crystallize in the cubic Y4PdGa12-type (Im-3m) which is a superstructure of the AuCu3-type (Pm-3m). The doubling of the cell parameters gives a = 8.593(1)angstrom, a = 8.579(1)angstrom and a = 8.611(1)angstrom for U, Np and Pu compounds, respectively. We report, for all the three compounds, noticeable enhanced value of the Sommerfeld coefficient gamma (up to 900 mJ mol(-1) K-2). Magnetic measurements reveal that U4PdGa12 orders antiferroinagnetically at T-N = 43 K with an effective moment mu(eff) = 3.40(1) mu B in the paramagnetic regime, in good agreement with the theoretical U3+ free ion moment. whereas both Np and Pu homologues do not present any phase transition down 2 K. (c) 2006 Elsevier B.V. All rights reserved.