MAGNETIC-RELAXATION IN UCU4+XAL8-X

A quasielastic neutron scattering study has been performed on UCu4+xAl 8-x, a system which reveals an alloying-induced transition from magnet ic order to heavy-fermion behavior. The magnetic response can be descr ibed by a broad quasielastic Lorentzian for all concentrations. No cry stal field excitations could be detected. Remarkably, the linewidth de creases with increasing hybridization strength and seems to be no meas ure of the Kondo lattice temperature T. In addition, electron spin re sonance (ESR) experiments were performed which revealed that, even in the heavy-fermion regime, spin fluctuations play an important role. Bo th experimental findings are in distinct contrast to cerium-based heav y fermion systems.