2-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 ord ered ground states. The pronounced non-Fermi-liquid behavior at x(c )c alls for a search for the relevant quantum critical fluctuations. Syst ematic measurements of the inelastic neutron scattering cross section S(q, omega) for x = 0.1 reveal rodlike features in the reciprocal ne p lane translating to two-dimensional (2D) fluctuations in real space. W e 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.