Magnetic and thermal properties of cubic SmCu₄X compounds (x = Ag, Au and Pd)

Measurements of magnetization M(H), susceptibility _χ(T), electrical resistivity ρ(T), and specific heat C(T) are performed on a new system SmCu₄X with X = Ag, Au and Pd. For all the three compounds, _χ(T) in paramagnetic state does not exhibit Curie-Weiss behavior. Whereas _χ(T) for the compounds with X = Ag and Au shows an antiferromagnetic ordering at 5.5 and 3.6 K, respectively, SmCu₄Pd behaves as a ferromagnet with T_C = 31 K. Sm ions appear to be near trivalent in the three compounds. The magnetic field dependence of C(T) around the transition temperature is analyzed qualitatively by molecular field theory for the three compounds. For SmCu₄Au, C(T) is insensitive to magnetic field and a large value of C/T, 500 mJ/mol K², remains at the zero-temperature limit in external fields of up to 8 T.