Crystal growth, structure, and physical properties of Ln(Ag, Al, Si)2 (Ln = Ce and Gd)

Single crystals of CeM2 and GdM2 (M = Ag, Al, and Si) were grown by the flux growth technique and characterized by means of single crystal x-ray diffraction, magnetic susceptibility, resistivity, and heat capacity measurements. CeM2 and GdM2 crystallize in the tetragonal I41/amd space group with the α-ThSi2 structure type with lattice parameters a ∼ 4.2 A and c ∼ 14.4 A. Curie-Weiss behavior is observed for both analogues with CeM2 ordering first ferromagnetically at 11 K with a second antiferromagnetic transition at 8.8 K while GdM2 orders antiferromagnetically at 24 K. Heat capacity measurements on CeM2 show two magnetic transitions at 10.8 and 8.8 K with an electronic specific heat coefficient, γ0, of ∼ 53 mJ K-2 mol-1. The entropy at the magnetic transition is less than the expected Rln2 for CeM2, reinforcing the assertions of an enhanced mass state and Kondo behavior being observed in the resistivity.