Absence of magnetic moments in plutonium

TL;DR

Extensive experimental investigations show no evidence of magnetic moments in plutonium at low temperatures, challenging theories that predict localized magnetic moments based on electron localization.

Contribution

The paper provides comprehensive experimental data refuting the presence of magnetic moments in plutonium, and reviews theoretical models in light of these findings.

Findings

No magnetic moments detected in plutonium experiments

Experimental results contradict theories predicting localized magnetic moments

Electron localization in calculations does not correspond to observed magnetic moments

Abstract

Many theories published in the last decade propose that either ordered or disordered local moments are present in elemental plutonium at low temperatures. We present new experimental data and review previous experimental results. None of the experiments provide any evidence for ordered or disordered magnetic moments (either static or dynamic) in plutonium at low temperatures, in either the alpha- or delta-phases. The experiments presented and discussed are magnetic susceptibility,electrical resistivity, NMR, specific heat, and both elastic and inelastic neutronscattering. Many recent calculations correctly predict experimentally observed atomic volumes, including that of delta-Pu. These calculations achieve observed densities by the localization of electrons, which then give rise to magnetic moments. However, localized magnetic moments have never been observed experimentally in Pu. A theory is needed that is in agreement with all the experimental observations. Two theories are discussed that might provide understanding of the ensemble of unusual properties of Pu, including the absence of experimental evidence for localized magnetic moments; an issue that has persisted for over 50 years.