Field-induced transition from non-Fermi-liquid state to heavy Fermion state in Ce_0.5La_0.5B₆

Measurements of the electrical resistivity, specific heat, and dHvA oscillations have been made on a cubic Kondo system Ce_0.5La_0.5B₆ with a Γ₈ ground state at very low temperatures. In the paramagnetic phase I which appears in lower fields, the electrical resistivity deviates from the formula ρ(T)=ρ(0)+AT² below ∼300 mK, implying an appearance of non-Fermi-liquid (NFL) state. In the field induced antiferromagnetic phase III, the large γ coefficient in the specific heat and the large coefficient A in the electrical resistivity have been found, indicating a heavy fermion (HF) state. The coefficient A diverges when the field approaches the phase III–phase I transition point. On the other hand, by increasing the Ce concentration phase IV with a long range order appears and a HF state is found to be formed there. We argue that the origin of the NFL behavior is related with the quadrupolar moment.