Effective-field theory of local-moment formation in disordered metals

We present a simple new effective-field theory for the metallic state of a disordered interacting Fermi liquid, taking into account its instability towards the formation of local-moment states. We find a generalization of the compensation theorem of the single-impurity Anderson model, namely that strongly localized magnetic instabilities occur even when the mean-field single-quasiparticle states are extended. The theory clarifies the understanding of recent thermodynamic and spin-resonance measurements in phosphorus-doped silicon.