  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.
