Single crystal growth and electronic state of new compounds RPt₂Cd₂₀(R = La-Nd, Sm)

We succeeded in growing five new single crystalline compounds RPt₂Cd₂₀(R = La, Ce, Pr, Nd, and Sm) by the Cd self-flux method. These compounds are found to crystallize in the cubic CeCr₂Al₂₀-type crystal structure by the X-ray diffraction using single crystals. We measured the electrical resistivity, magnetic properties, and specific heat for all compounds. The resistivity for R = Ce, Nd, and Sm indicates an abrupt decrease, which might correspond to a magnetic transition. It is suggested that the ground state of CePt₂Cd₂₀is Γ₇doublet from the magnetization measurement. The magnetization of PrPt₂Cd₂₀shows a metamagnetic behavior at 1.6 T in the paramagnetic state, which could be due to the crystalline electric field effect with non-Kramers Γ₃doublet or Γ₁singlet ground state. The contribution of optical phonon modes to the lattice specific heat is discussed in LaPt₂Cd₂₀.