OBSERVATION OF LOW-ENERGY MAGNETIC RESPONSE IN THE HEAVY-FERMION COMPOUND UBE(13)

Inelastic-neutron-scattering experiments have been used to examine the low-frequency (< 2 meV) response of polycrystalline samples of the heavy-fermion UBe13. A quasielastic response with a characteristic linewidth of 1.5 meV for T > 1 K is found. Surprisingly we found no anomalous dependence of this response on q, the reduced reciprocal lattice vector. The strength of the response corresponds to approximately 60% of the bulk susceptibility, and it scales with the latter for 1.5 < T < 30 K. Taking into account earlier experiments the total response function for UBe13 thus contains two components, one with a linewidth of 1.5 meV and the other [A. 1. Goldman et al., Phys. Rev. B 33, 1627 (1986)] with a linewidth of approximately 13 meV. The weight is approximately evenly divided between the two. UBe13 is therefore similar to UPt3 in that the-magnetic response functions exist on two quite different energy scales. This appears different from Ce-based heavy fermions, and is not yet understood.