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

TL;DR

This study uses LDA+DMFT calculations to investigate why PuAm alloys lack magnetic moments, revealing a complex interplay of effects that stabilize a consistent coherence scale around 800K.

Contribution

It demonstrates how multiple competing effects in PuAm alloys lead to a stable coherence scale, emphasizing the importance of DMFT self-consistency and atomic multiplet splittings.

Findings

Coherence scale around 800K independent of alloy composition

Volume expansion and hybridization effects compensate each other

DMFT self-consistency is crucial for accurate results

Abstract

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.