Metamagnetic behavior and effect of pressure on the electronic state in heavy-fermion compound YbRh₂Zn₂₀

We measured the magnetic susceptibility, high-field magnetization, magnetoresistance, specific heat, and Hall coefficient, together with the electrical resistivity under high pressures and magnetic fields, for the heavy-fermion compound YbRh₂Zn₂₀ with the cubic CeCr ₂Al₂₀-type structure. The metamagnetic behavior was observed at Hm =65 kOe for the magnetic field along the h100i direction below Txmax = 5:3 K, at which the temperature of the magnetic susceptibility indicates a broad maximum. The coefficient A of the T² dependence of electrical resistivity ρ = ρ0 + AT² and the electronic specific heat coefficient C=T possess a broad maximum at H_m. The metamagnetic field H_m is found to decrease with increasing pressure and to become zero at a critical pressure Pc ≠ 5:2 GPa. Correspondingly, the A value increases drastically in magnitude, and the Fermi liquid relation is no longer satisfied at 5.2 GPa in zero magnetic field, implying a non-Fermi liquid state. On the other hand, at magnetic fields ofH >20 kOe, the low-temperature resistivity exhibits a T² dependence even at 5.2 GPa. The A coefficient decreases rapidly with increasing magnetic field. These results indicate that an electronic state at 5.2 GPa corresponds to the quantum critical point.