Heavy Fermion State in YbIr₂Zn₂₀

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We measured the high-field magnetization and de Haas–van Alphen (dHvA) oscillations for YbIr₂Zn₂₀ with a cubic crystal structure, together with the electrical resistivity and magnetic susceptibility. The magnetic susceptibility χ with an effective magnetic moment of Yb³⁺ becomes temperature-independent at low temperatures, with a broad peak at T_χmax=7.4 K for H||‹110›. The corresponding magnetization indicates a metamagnetic transition at H_m=120 kOe, consistent with a T_χmax vs H_m relation in the Ce- and U-based heavy fermion compounds. The large cyclotron masses of 4–27 m₀ are detected in the dHvA experiment, and are found to be reduced at magnetic fields higher than H_m=120 kOe. The resistivity follows the Fermi liquid relation ρ=ρ₀+AT² under magnetic field, and the \\sqrtA value is also found to have a maximum at H_m as a function of magnetic field. From the present experimental results, together with the results of 4f-itinerant energy band calculations, the 4f electrons are found to contribute to the heavy fermion state in YbIr₂Zn₂₀.