Neutron-Diffraction Study of the Kondo Effect in Cu-Fe

Polarized-neutron techniques have been used to investigate the Kondo effect in a 1250-ppm Cu-Fe alloy. The angular dependence of the magnetic-scattering amplitude, measured at 4.22^∘{}K, was found to be of $3d$ electronic character and the localized susceptibility, as determined from the neutron-diffraction observations, was found to agree in absolute magnitude as well as in its temperature dependence with the total magnetic susceptibility measured on the same samples. This observation implies the absence of any large contribution to the bulk susceptibility by the field-induced polarization in the compensating conduction-electron cloud. The characteristic temperature, obtained by fitting the data to a Curie-Weiss law, was found to be (5.3 ±{} 1.6) ^∘{}K. By fitting the data to the predictions of the spin-fluctuation model the localized-spin-fluctuation lifetime was found to be approximately 10^-12 sec; the corresponding characteristic temperature is 6 ^∘{}K with an estimated standard deviation of 2 ^∘{}K.