Metamagnetic transition in heavy fermion compounds YbT₂Zn ₂₀ (T : Co, Rh, Ir)

We measured the magnetization in high magnetic fields up to 500kOe, together with the magnetic susceptibility, ac-susceptibility and magnetoresistance for heavy fermion compounds YbT₂Zn₂₀ (T : Co, Rh, Ir). The metamagnetic behaviour or an abrupt nonlinear increase of magnetization was observed at the magnetic field H_m at temperatures lower than a characteristic temperature T_χmax below which the magnetic susceptibility becomes almost constant : T_χmax = 7.4K and H_m = 97kOe in YbIr₂Zn₂₀, T _χmax = 5.3K and H_m = 64kOe in YbRh₂Zn ₂₀, and T_χmax = 0.32K and H_m = 6kOe in YbCo₂Zn₂₀. From the present data and the data in several Ce and U heavy fermion compounds, a simple relation between T_χmax and H_m was obtained : H_m(kOe) = 15T_χmax(K) .