Screening of magnetic moments in PuAm alloy : LDA+DMFT study

The puzzling absence of Pu magnetic moments in a PuAm environment is explored using the self-consistent Dynamical Mean Field Theory (DMFT) calculations in combination with the Local Density Approximation. We argue that delta-Pu -Am alloys provide an ideal test bed for investigating the screening of moments from the single impurity limit to the dense limit. Several important effects can be studied: volume expansion, shift of the bare Pu on-site f energy level, and the reduction of the hybridization cloud resulting from the collective character of the Kondo effect in the Anderson lattice. These effects compensate each other and result in a coherence scale, which is independent of alloy composition, and is around 800K. We emphasize the role of the DMFT self-consistency condition, and multiplet splittings in Pu and Am atoms, in order to capture the correct value of the coherence scale in the alloy.