Kondo effect in an antiferromagnetic metal: Renormalization group analysis and a variational calculation

We study the fate of a spin-1/2 impurity in the itinerant antiferromagnetic metallic phase via a renormalization group analysis and a variational calculation. The local moment-conduction electron interaction Hamiltonian in an antiferromagnetic metal is spin nonconserving. We show that for a general location of the impurity, the Kondo singularities still occur, but the ground state has a partially unscreened moment. We calculate the magnitude of this residual moment and the variation of the spin polarization with energy for a substitutional impurity as a function of the staggered magnetization. The usual Kondo effect only occurs if the impurity is placed at points where the magnetization is zero.