Samarium

Uses

Samarium’s most valuable role is in samarium-cobalt magnets, a class of rare-earth permanent magnets developed before the now-more-common neodymium magnets. They’re not as strong at room temperature, but they resist demagnetizing at high temperatures and resist corrosion, which is why they turn up in aerospace components, precision motors, and headphones or microphones that need a small, heat-tolerant magnet. Samarium compounds are also reasonably good at absorbing neutrons, so they’re used in some nuclear reactor control rods alongside elements like europium and gadolinium.

Medicine is samarium’s other notable application: a radioactive isotope, samarium-153, is bonded to a compound that seeks out bone tissue and used to relieve pain in patients whose cancer has spread into their bones. This lets clinicians deliver targeted radiation to affected areas rather than treating the whole body.

History

Samarium was identified in 1879 by French chemist Paul-Émile Lecoq de Boisbaudran, who detected its distinctive spectral lines in a sample derived from the mineral samarskite. Like several other lanthanides, it took more work over the following years to confirm it as a genuinely separate element and eventually isolate it in a purer form, since minerals like samarskite contain a tangle of closely related rare earths. Its name traces back to the mineral it was found in, which had earlier been named after Vasili Samarsky-Bykhovets, a Russian mining official — making samarium one of the first elements named, indirectly, after a real person.