Magnetic-field tuning of quantum critical fluctuations in CeCu5.9Au0.1

The magnetic field dependence of the quantum critical fluctuations close to the antiferromagnetic transition in CeCu5.9Au0.1 is investigated directly by neutron scattering at TAS7 in Riso in a horizontal magnet. The butterfly-shaped critical wave vector region in the a{*}c{*}-plane persists up to H = 1.8 T (Hparallel toc) and the magnetic spectrum can be represented by the same function used for 0 T, including the unusual exponent alpha = 0.75. The field only changes the dynamics like an effective temperature T-eff = (T-2 + (muH/k(B))(2))(0.5) with a moment mu = 1.3mu(beta). This result is entirely consistent with and complements the 0 T neutron scattering and the uniform magnetization data, which are successfully described by E/T and H/T scaling properties, respectively, establishing the unusual non-Fermi-liquid behavior in this heavy fermion compound. (C) 2002 Elsevier Science B.V. All rights reserved.