Scientists discover why plutonium doesn't stick to magnets

The discovery proves that plutonium's magnetism is not necessarily missing, only sporadic.
By Brooks Hays   |   July 13, 2015 at 10:01 AM

LOS ALAMOS, N.M., July 13 (UPI) -- Plutonium is definitely a metal. But unlike all other metals, it cares little for magnets and their so-called magnetism. In fairness, magnets care little for plutonium and its standoffishness.

But why don't magnets and plutonium get along? Scientists have been befuddled by the absence of attraction for some time. New research, however, has revealed an answer. The key to their disassociation lies in metal's electrons.

Electrons circle the nucleus of an atom in shells or orbitals, some closer and some slightly farther out. Each shell has a maximum number of electrons it can contain. For metals, the max capacity of their atoms' outer shell is fixed.

In a stable, grounded state (uninfluenced by heat, electricity or other outside forces), the number of electrons in metals like copper and iron is always the same.

But when scientists took a closer look at the outer orbitals of plutonium atoms, using a method called neutron spectroscopy, they found a less predictable population of electrons -- sometimes four, sometimes five, sometimes six, sometimes more.

The constantly rotating cast of outer electrons make it impossible for plutonium and its unpaired electrons to line up with an abutting magnetic field.

The discovery proves that plutonium's magnetism is not necessarily missing, only sporadic; it also explains why the metal is so unstable.

"It provides a natural explanation for plutonium's complex properties and in particular the large sensitivity of its volume to small changes in temperature or pressure," Marc Janoschek, a researcher the Department of Energy's Los Alamos National Laboratory, said in a press release.

Janoschek is the lead author of a new paper on the discovery, published in the journal Science Advances.

More than just revealing plutonium's atomic secrets, the new research will help scientists more accurately predict and model the behavior of new materials.

"A predictive theory of materials is a big deal because we eventually will be able to simulate and predict properties of materials on a computer," Gabriel Kotliar, a physics professor at Rutgers, told LiveScience. "For radioactive materials like plutonium, that's a lot cheaper than doing an actual experiment."

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