The Problem of Scattering by Magnetic Impurities in Metals

The ``s-d'' model of interaction of a free electron gas with a magnetic impurity is treated by the methods of scattering theory. Older transport-theory results are reviewed, and two additional measurements are proposed: frequency dependence of the resistivity (at low frequencies), and the Hall coefficient. The latter should show a broad maximum. It is suggested that because the ``s-d'' model leads to strong coupling effects, it is necessary to return to fundamentals. A preliminary indication of how this might be done is given at the end of the paper.