Transition from the Magnetic to the Nonmagnetic Transitional Impurity State in Copper-Aluminum Alloys: The Nature of the Nonmagnetic State
The static susceptibility of Mn and Fe impurities has been measured in several liquid copper-aluminum alloys, ranging in concentration from 80 at.% copper to 80 at.% aluminum. The impurity susceptibility in the copper-rich alloys is well described by Kondo perturbation theory. The parametric fit indicates that the zero-order state is the same as in pure copper and that TK rises rapidly with aluminum concentration. In the aluminum-rich alloys the susceptibility of both impurities increases rapidly with temperature, in sharp contrast to the constant susceptibility found for the low-temperature "nonmagnetic" impurity and in contrast to the predictions of both the Kondo bound-state model and the weak-coupling-spin-fluctuation model which have been suggested for this impurity state. The latter model cannot be made consistent with the data, but it is speculated that the Kondo model may display anomalies similar to those found experimentally if the bound state is disrupted by thermal scattering.