Cu Nuclear Magnetic Relaxation Studies of the Antiferromagnetic Heavy-Electron Compound UCu5

Abstract

Cu nuclear magnetic relaxation rate 1/ T 1 has been measured in the antiferromagnetic heavy-electron compound UCu 5 ( T N =15 K) in the paramagnetic state under zero external field by NQR technique. At high temperatures 1/ T 1 tends toward a constant, whereas on approaching T N it shows marked critical divergence, which has been found close to T 1 T ∝( T - T N ) 0.4 . An analysis has been made in terms of an exchange-coupled Kondo-impurity model, and the divergent behavior has been shown to be not incompatible with the model. At high temperatures, neglecting the q -dependences in χ( q , ω) and taking account of the neutron quasielastic linewidth at 50 K, the relaxation rate of U moments has been deduced. The large relaxation rate and its strong temperature-dependence suggest both the strong hybridization between 5f and conduction electrons and the dominance of the single-site dynamics in the U moment relaxation in UCu 5 .