Heavy-fermion behavior, crystalline electric field effects, and weak ferromagnetism in SmOs4Sb12 -: art. no. 104402

The filled skutterudite compound SmOs4Sb12 was prepared in single-crystal form and characterized using x-ray diffraction, specific-heat, electrical resistivity, and magnetization measurements. The SmOs4Sb12 crystals have the LaFe4P12-type structure with lattice parameter a=9.3085 A. Specific-heat measurements indicate a large electronic specific-heat coefficient of approximate to 880 mJ/mol K-2, from which an enhanced effective mass m*approximate to 170m(e) is estimated. The specific-heat data also suggest crystalline electric field (CEF) splitting of the Sm(3+)J=5/2 multiplet into a Gamma(7) doublet ground state and a Gamma(8) quartet excited state separated by similar to 37 K. Electrical resistivity rho(T) measurements reveal a decrease in rho(T) below similar to 50 K that is consistent with CEF splitting of similar to 33 K between a Gamma(7) doublet ground state and Gamma(8) quartet excited state. Specific-heat and magnetic susceptibility measurements display a possible weak ferromagnetic transition at similar to 2.6 K, which could be an intrinsic property of SmOs4Sb12 or possibly due to an unknown impurity phase.