SCALING OF MAGNETIC FLUCTUATIONS NEAR A QUANTUM PHASE-TRANSITION

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