Samarium · element 62
The magnet metal that keeps working when hot, and the first element named, indirectly, after a person
Key facts
Ask an engineer about samarium and they will probably mention magnets. Samarium cobalt magnets were the first of the modern super strong permanent magnets, and although neodymium magnets have since overtaken them in raw strength, samarium cobalt still wins where things get hot. That single property keeps this otherwise obscure lanthanide in demand for aerospace, motors and sensors.
Samarium is a silvery white metal that slowly tarnishes in air. It is moderately hard, forms pale yellow salts in its usual +3 state, and, unusually for a lanthanide, can also be coaxed into a +2 state that chemists exploit as a powerful reducing agent. Its name has a roundabout origin: it comes from the mineral samarskite, which was itself named after a Russian mining official called Vasili Samarsky-Bykhovets.
Where it is found
Samarium never appears as a free metal in nature. It is locked up with the other rare earths in minerals such as monazite and bastnäsite, where it typically makes up a small percentage of the total rare earth content. It is recovered in China, the United States and Australia as one product among many from the same processing lines that yield neodymium and cerium.
In the Earth's crust it is roughly as common as tin, so it is not truly rare. The challenge is separation. The lanthanides are chemically so alike that pulling one from its neighbours takes many stages of solvent extraction or ion exchange.
How it was discovered
In the nineteenth century, chemists studying a substance called didymium, which they thought was an element, kept finding it would not behave consistently. In 1879 the French chemist Paul-Émile Lecoq de Boisbaudran examined a sample extracted from samarskite and saw spectral lines that did not belong to any known element. He had found samarium, and he named it after the mineral.
The mineral itself carried the name of Samarsky-Bykhovets, who had allowed geologists access to specimens from the Urals. In this way samarium became the first chemical element with a name traceable to a living person, even if the honour arrived second hand.
What we use it for
Samarium cobalt magnets are the headline use. They resist demagnetisation extremely well and keep working at temperatures of around 300 °C where neodymium magnets fail. That makes them the choice for jet engine sensors, satellite components, high performance motors, microwave tubes and the pickups in many electric guitars and headphones.
The isotope samarium-153, attached to a phosphonate molecule, is used in medicine to relieve the pain of cancer that has spread to bone. The compound seeks out bone, and the short range beta radiation targets the tumour sites.
In nuclear reactors samarium plays a quieter role. Samarium-149 absorbs neutrons very strongly, so it is used in control rods, and it also builds up as a fission product inside fuel, where engineers must account for its effect on the reaction. In the laboratory, samarium(II) iodide is a favourite reagent for organic chemists because it donates electrons cleanly in delicate syntheses.
Reading the numbers
Samarium melts at about 1072 °C and boils at roughly 1900 °C, a relatively short liquid range for a metal. Its density of 7.52 grams per cubic centimetre puts it just below iron.
Its electron configuration is [Xe] 4f6 6s2. The 4f electrons sit deep inside the atom and take little part in bonding, which is why all the lanthanides behave so alike and why samarium normally forms +3 ions. Reaching six electrons in the 4f shell also gives samarium access to a +2 state that is stable enough to be useful, a hint of the half filled shell that europium reaches next. Its first ionisation energy of around 545 kJ/mol and electronegativity of 1.17 are typical of a reactive, electropositive metal. Its atomic mass of 150.36 is not a whole number because natural samarium is a blend of seven isotopes, two of which are very weakly radioactive.
Safety and the environment
Samarium metal and its common compounds are of low toxicity. The dust can ignite if finely divided, as with most rare earth metals, and should be kept away from sparks. Natural samarium contains isotopes such as samarium-147 that are radioactive, but their half-lives are so enormous that the radiation is negligible and requires no special handling.
The environmental cost of samarium lies mainly in mining and separating rare earths, which produces acidic waste and can release naturally occurring radioactive thorium from monazite. Samarium cobalt magnets are increasingly collected from scrap for recycling.
Did you know?
- Samarium-147 decays so slowly, with a half-life around a hundred billion years, that geologists use it to date some of the oldest rocks on Earth and meteorites from the early solar system.
- Samarium cobalt magnets keep their strength at temperatures where neodymium magnets lose theirs, which is why they are used in jet engines and satellites.
- The element is named after the mineral samarskite, which honours a Russian mining official, making samarium the first element named, indirectly, after a person.
- Samarium-149 absorbs neutrons so effectively that nuclear engineers must allow for it building up inside reactor fuel as the uranium splits.
- Samarium(II) iodide, known to organic chemists as Kagan's reagent, is a deep blue solution used to make carbon to carbon bonds gently.
More in the lanthanides
The nearest neighbours of samarium in the family, by atomic number.
See all 15 lanthanides on one page, or browse all 118 elements.
Compare Samarium with another element
Each comparison has a side-by-side data table and a plain-English summary of the differences.
Frequently asked questions
What is samarium used for?
Its biggest use is in samarium cobalt permanent magnets, which stay strongly magnetic at high temperatures and are found in aerospace equipment, motors and guitar pickups. It is also used in a radioactive drug that eases pain from bone cancer and as a neutron absorber in nuclear reactors.
Is samarium radioactive?
Natural samarium contains a few isotopes that are radioactive, but their half-lives are measured in billions to trillions of years, so the radiation is far too weak to matter in everyday use. The metal is handled like any other rare earth without radiation precautions.
Why are samarium cobalt magnets better than neodymium magnets?
They are not stronger, but they tolerate heat much better and resist corrosion and demagnetisation. Neodymium magnets are cheaper and more powerful at room temperature, so samarium cobalt is chosen when the magnet must work at several hundred degrees.
How did samarium get its name?
Lecoq de Boisbaudran discovered it in 1879 in the mineral samarskite and named it after that mineral. Samarskite had earlier been named after Vasili Samarsky-Bykhovets, a Russian mine official, so the element carries his name at one remove.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Samarium reference article. Spotted an error? Tell us.