Robustness of non-Fermi-liquid behavior near the ferromagnetic critical point in clean ZrZn₂

Electrical resistivity ρ of a weak itinerant ferromagnet ZrZn ₂ with a low residual resistivity ρ₀ ≃ 0.46 μΩcm was measured under hydrostatic pressure P up to 3.2 GPa. T ²-behavior of ρ, a hallmark of Fermi liquid, was not observed down to 1 K not only at around the ferromagnetic critical point P_c ∼ 2 GPa but over an entire pressure range investigated. The temperature dependence of ρ at low temperatures evolved from T^5/3 in the ferromagnetic phase to T^3/2 in the paramagnetic phase. This change, however, was very weak and it was hard to capture the signature of critical point in the resistivity. Such a breakdown of Fermi liquid over a remarkably wide phase space indicates the lack of some ingredient in the description of magnetic quantum critical point in clean metals.