Strong valence fluctuation effects in SmT r2Al20 (T r = Ti, V, Cr)

We present a single-crystal study of low-temperature magnetism and transport in SmTr2Al20 (Tr = Ti, V, and Cr). Strong valence fluctuation is manifested as Kondo effects, including a large Sommerfeld coefficient., a weak temperature dependence of magnetic susceptibility, and a-ln T dependent resistivity. All the systems order antiferromagnetically at T-N = 6.4 K (Ti), 2.9 K (V), and 1.8 K (Cr). A systematic change in the susceptibility, specific heat, and resistivity indicates that stronger c-f hybridization in SmV2Al20 and SmCr2Al20 than in SmTi2Al20 suppresses T-N and induces the valence fluctuations and, moreover, field-insensitive heavy fermion states.