Plutonium's 'Missing' Magnetism Discovered: Neutrons Reveal Strange Properties of Element

It turns out that plutonium has magnetism-something that scientists have long theorized but haven't been able to prove. The new discovery holds great promise for materials, energy and computing applications.

Plutonium was first produced in 1940. Its unstable nucleus allows it to undergo fission, which makes it useful for nuclear fuels and nuclear weapons. In addition, an electronic cloud surrounds the plutonium and is equally unstable; this makes plutonium the most electronically complex element in the periodic table.

Conventional theories have successfully explained plutonium's complex structural properties. However, these theories also predict that plutonium should order magnetically. This is in stark contrast with experiment, which had found no evidence for magnetic order in plutonium.

In this latest study, the researchers used neutron scattering to make the first direct measurements of a unique characteristic of plutonium's fluctuating magnetism. Plutonium isn't devoid of magnetism. In contrast, its magnetism is in a constant state of flux, which makes it nearly impossible to detect.

"Plutonium sort of exists between two extremes in its electronic configuration-in which we call a quantum mechanism superposition," said Marc Janoschek, one of the researchers, in a news release. "Think of the one extreme where the electrons are completely localized around the plutonium ion, which leads to a magnetic moment. But then the electrons go to the other extreme where they become delocalized and are no longer associated with the same ion anymore."

The new findings provide a natural explanation for plutonium's complex properties. More specifically, it reveals why there's the large sensitivity of its volume to small changes in temperature or pressure.

The findings don't only reveal a microscopic explanation, though. They also suggest an improved understanding of complex, functional materials that frequently are characterized by similar electronic dichotomies.

The findings are published in the journal Science Advances.

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