Disorder and the quantum critical point in UCu5-xPdx

We have measured the magnetization of UCu5-xPdx (x = 0.7, 1, 1.5, 2) in fie lds H as large as 30 T and for temperatures between 1.4 K and 150 K. A comp osition- and temperature dependent characteristic field H*(x, T) is identif ied, which separates two different non-Fermi liquid scaling regimes, presen t even in zero field. For H greater than or equal to H*(x, T), composition- independent scaling is found, while for H less than or equal to H*(x, T), d ifferent exponents are found for each composition. This second phase is cen tred in temperature and composition around the x = 1, T = 0 critical point, and we argue that it is consistent with the presence of a Griffiths phase.