Two-dimensional fluctuations at the quantum-critical point of CeCu6-xAux

The heavy-fermion system CeCu6-xAux exhibits a quantum-critical point at x(c) approximate to 0.1 separating nonmagnetic and magnetically ordered ground states. The pronounced non-Fermi-liquid behavior at x(c )calls for a search for the relevant quantum critical fluctuations. Systematic measurements of the inelastic neutron scattering cross section S(q, omega) for x = 0.1 reveal rodlike features in the reciprocal ne plane translating to two-dimensional (2D) fluctuations in real space. We find 3D magnetic ordering peaks for x = 0.2 and 0.3 located on these rods which hence can be viewed as 2D precursors of 3D order.