Scaling of magnetic fluctuations near a quantum phase transition

We use inelastic neutron scattering to measure the magnetic fluctuations in a single crystal of the heavy fermion alloy CeCu5.9Au0.1 close to the antiferromagnetic quantum critical point. The energy (E), wave vector (Q), and temperature (T) dependent spectra obey E/T scaling at Q near (1,0,0). The neutron data and earlier bulk susceptibility are consistent with the form chi(-1) similar to f(Q) + (-iE + aT)(alpha), with an anomalous exponent alpha approximate to 0.8 not equal 1. We confirm the earlier observation of quasilow dimensionality and show how both the magnetic fluctuations and the thermodynamics can be understood in terms of a quantum Lifshitz point.