NEARLY SINGULAR MAGNETIC FLUCTUATIONS IN THE NORMAL-STATE OF A HIGH-T-C CUPRATE SUPERCONDUCTOR

Polarized and unpolarized neutron scattering was used to measure the w ave vector-and frequency-dependent magnetic fluctuations in the normal state (from the superconducting transition temperature, T-c = 35 kelv in, up to 350 kelvin) of single crystals of La1.86Sr0.14CuO4. The peak s that dominate the fluctuations have amplitudes that decrease as T-2 and widths that increase in proportion to the thermal energy, k(B)T (w here k(B) is Boltzmann's constant), and energy transfer added in quadr ature. The nearly singular fluctuations are consistent with a nearby q uantum critical point.