Third-order magnetic susceptibility and quadrupolar order parameter of Kondo-lattice compound Ce₃Pd₂₀Ge₆

We present a report on crystalline-electric-field effects observed in the electrical resistivity and the specific heat of Ce₃Pd₂₀Ge₆, which are discussed within an energy level scheme of the Γ₈ ground state and the Γ₇ excited state at 50 K for both inequivalent crystallographic sites of Ce atom. The third-order magnetic susceptibility was deduced from the magnetization measurement in the paramagnetic phase of a single-crystalline sample in magnetic fields applied along [0 0 1] and [1 1 1]. In order to explain the temperature dependence of the third-order magnetic susceptibility along [0 0 1], a positive total quadrupolar pair interaction constant of 22 mK is required in addition to a small antiferromagnetic exchange interaction, thereby suggesting ferroquadrupolar ordering with the Γ₃ symmetry in this compound.