PARAMAGNETIC SCATTERING FROM THE VALENCE-FLUCTUATION COMPOUND YBAL3

Results of a reinvestigation of paramagnetic scattering from YbAl3 are presented- They confirm earlier observations of the gaplike spectral response at low temperatures (5 K), viz., a low level of magnetic scattering up to approximately 30 meV followed by a sharp rise peaking on approximately 32 meV forming a ridge to the bulk of the spectral response lying beyond. The gap in the magnetic response smears out rapidly with increasing temperature such that for temperatures close to and above the maximum in the bulk susceptibility (approximately 130 K), the observed scattering is indistinguishable from a quasielastic distribution, viz., a broad Lorentzian of half-width approximately 35 meV centered on zero energy. Measurements performed using low-energy neutrons under closely similar experimental conditions as in another reported neutron study of YbAl3 demonstrate the strong influence of phonon scattering, misinterpreted by the authors of that investigation as representing a transition to a Kondo resonance around approximately 10 to 12 meV at temperatures between 120 and 50 K.