Samarium (symbol: Sm, atomic number: 62) is a moderately hard silvery-white lanthanide metal best known as the critical element in samarium-cobalt (SmCo) permanent magnets — the only class of magnet that retains full magnetic performance above 300°C. Produced almost entirely in China, samarium is subject to export controls that have drawn increasing attention from defence procurement agencies in the US and Europe.
What Is Samarium? Key Properties
Samarium belongs to the lanthanide series of rare earth elements. At 7 parts per million (ppm) in the Earth’s crust, it is more abundant than gold or silver, though commercially viable concentrations are limited to a handful of deposit types — primarily monazite and bastnäsite ores.
Unlike most lanthanides, samarium exists stably in both +3 and +2 oxidation states. The +2 state, expressed as Sm²⁺ compounds such as samarium(II) iodide (SmI₂), is a powerful reducing agent widely used in organic synthesis. The more common Sm³⁺ state governs its behaviour in magnets, ceramics, and nuclear applications.
| Property | Value |
|---|---|
| Atomic number | 62 |
| Symbol | Sm |
| Atomic weight | 150.36 g/mol |
| Melting point | 1,072°C |
| Boiling point | 1,794°C |
| Density | 7.52 g/cm³ |
| Crustal abundance | ~7 ppm |
| Primary ore minerals | Monazite, bastnäsite |
| Dominant producer | China (Baotou) |
Samarium ignites spontaneously in air above 150°C in powder form and oxidises slowly at room temperature, developing a yellow-grey surface layer. Bulk metal is stored under inert gas or mineral oil for this reason.
What Is Samarium Used For? Primary Applications
Samarium-Cobalt Permanent Magnets
The dominant commercial use of samarium is in samarium-cobalt (SmCo) permanent magnets, produced in two principal compositions: SmCo₅ and Sm₂Co₁₇. SmCo magnets produce permanent magnetisation roughly 10,000 times that of iron. Their defining advantage over the more powerful neodymium-iron-boron (NdFeB) magnets is thermal stability: SmCo retains full magnetic performance to above 700°C versus 300–400°C for NdFeB grades. This makes SmCo the standard choice for jet engine actuators, missile guidance systems, satellite components, and high-speed motorsport motors where operating temperatures exceed NdFeB limits.
A single F-35 fighter jet contains approximately 23 kg of samarium-cobalt magnets. US and European procurement agencies have flagged SmCo supply security as a priority concern given China’s near-total control of samarium refining. The full landscape of manufacturers is covered in the Top 10 Rare Earth Magnet Manufacturers guide.
Nuclear Reactor Control
The isotope samarium-149 (¹⁴⁹Sm) has a neutron-capture cross section of 41,000 barns — one of the highest of any stable nuclide. It is incorporated into nuclear reactor control rods, where it regulates fission chain reactions by absorbing thermal neutrons. ¹⁴⁹Sm also builds up as a fission product during normal reactor operation, reaching equilibrium concentration after approximately 500 hours. Unlike xenon-135, which decays rapidly after shutdown, ¹⁴⁹Sm is stable and its poisoning effect persists, requiring explicit accounting in reactor design.
Radiopharmaceutical: Samarium-153 Lexidronam
The synthetic radioisotope samarium-153 (¹⁵³Sm) is the active component of samarium (¹⁵³Sm) lexidronam (trade name: Quadramet), an injectable drug used to relieve severe bone pain in patients with metastatic cancers including prostate, breast, and lung cancer, and osteosarcoma. ¹⁵³Sm is chelated with EDTMP to direct uptake selectively to bone tissue, where its beta emissions destroy cancer cells. Half-life is 46.3 hours.
Optical Glass and Ceramics
Samarium oxide (Sm₂O₃) is added to specialty optical glass to increase absorption of infrared radiation, improving performance in infrared cameras, laser optics, and precision lenses. It is also used as a catalyst in organic chemistry — particularly for dehydration and dehydrogenation of alcohols — and as a minor additive in ceramic formulations.
Chemical Synthesis
Samarium(II) iodide (SmI₂) is one of the most widely used single-electron reducing agents in synthetic organic chemistry. It is applied in carbon-carbon bond-forming reactions including the Barbier reaction, Reformatsky-type couplings, and a range of natural product total syntheses. SmI₂ reactions typically proceed under mild conditions in tetrahydrofuran at room temperature.
Discovery and Name Origin
Understanding what is samarium requires some historical context: it was isolated in 1879 by French chemist Paul-Émile Lecoq de Boisbaudran through spectroscopic analysis of the mineral samarskite. The mineral was named after Russian mining official Vassili Samarsky-Bykhovets, who had granted German mineralogists access to Ural ore samples in the 1840s. Samarium thus holds the distinction of being the first chemical element named — indirectly — after a real person.
Samarium Supply Chain and Geopolitics
China produces effectively all of the world’s refined samarium, with processing concentrated at Baotou in Inner Mongolia. World samarium resources are estimated at approximately 2 million tonnes; producing nations include China, the United States, Australia, Brazil, India, and Sri Lanka, but refining outside China is negligible in commercial terms.
Western dependence on a single production point has been a known vulnerability since the closure of a key samarium processing plant in La Rochelle, France in 1994 — a facility that had served NATO defence supply chains for two decades. China imposed export controls on samarium alongside other rare earths during the 2025 tariff dispute with the United States, directly affecting defence industrial supply lines. The broader risk context is covered in the Top 10 Rare Earth Supply Chain Risks analysis.
Samarium is typically sold as samarium oxide (Sm₂O₃). Separating samarium from mixed rare earth concentrates involves solvent extraction and requires close to 100 individual processing steps using concentrated acids — a process where Chinese facilities hold significant cost and scale advantages over any prospective Western entrant. Production statistics are published annually by the USGS National Minerals Information Center, with market data also maintained by the Minor Metals Trade Association.
Samarium vs Neodymium: Magnet Comparison
The two dominant rare earth permanent magnet systems — SmCo and NdFeB — address different applications. NdFeB produces higher maximum energy product and dominates EV traction motors, wind turbine generators, and consumer electronics. SmCo commands the high-temperature and defence market where NdFeB fails above 300–400°C. SmCo also requires no dysprosium or terbium additions to maintain coercivity at elevated temperatures — a supply chain advantage given HREE pricing volatility. See current neodymium pricing for NdFeB input cost context.
What Is Samarium? Key Facts Summary
| Category | Detail |
|---|---|
| Element classification | Lanthanide (light rare earth element) |
| Primary application | SmCo permanent magnets (aerospace, defence, motorsport) |
| Nuclear application | Control rods (¹⁴⁹Sm neutron absorber, 41,000 barns cross section) |
| Medical application | Samarium-153 lexidronam (bone cancer pain relief) |
| Key chemical reagent | SmI₂ — single-electron reductant in organic synthesis |
| Dominant producer | China (~100% of refined supply, Baotou) |
| Strategic status | US and EU critical mineral; Chinese export controls imposed 2025 |
| Discovery | 1879, Paul-Émile Lecoq de Boisbaudran (France) |
| Named after | Vassili Samarsky-Bykhovets — first element named after a real person |
This article is for informational purposes only and does not constitute investment advice.
What is samarium used for?
Samarium’s primary industrial use is in samarium-cobalt (SmCo) permanent magnets, which retain full magnetic performance above 700°C — making them essential for jet engines, missile guidance systems, and defence electronics where neodymium magnets fail. Additional uses include nuclear reactor control rods (samarium-149), bone cancer radiotherapy (samarium-153 lexidronam), specialty optical glass, and organic chemical synthesis via samarium(II) iodide.
What is samarium and how is it classified?
Samarium is a lanthanide rare earth element with the chemical symbol Sm and atomic number 62. It is a moderately hard silvery metal with a crustal abundance of approximately 7 ppm — more common than gold or silver. It is classified as a light rare earth element and is listed as a critical mineral by the US and EU due to its defence and energy applications.
Why are samarium-cobalt magnets used instead of neodymium magnets?
Samarium-cobalt (SmCo) magnets retain their magnetic properties above 700°C, versus 300–400°C for neodymium-iron-boron (NdFeB) grades. This makes SmCo the standard for aerospace actuators, satellite systems, and high-performance motorsport motors where operating temperatures exceed NdFeB limits. SmCo also requires no dysprosium or terbium additions to maintain coercivity at heat, removing that supply chain dependency.
Where does samarium come from?
Samarium occurs in monazite and bastnäsite ores, found in China, the United States, Australia, Brazil, India, and Sri Lanka. China dominates the supply chain at every stage — mining, separation, and refining — with processing concentrated at Baotou in Inner Mongolia. Refined samarium outside China is commercially negligible. China imposed export controls on samarium in 2025 during the US-China tariff dispute.
What is samarium-153 and what is it used for?
Samarium-153 (¹⁵³Sm) is a synthetic radioactive isotope used in the drug samarium (¹⁵³Sm) lexidronam (Quadramet). Chelated with EDTMP and injected intravenously, it targets bone tissue and delivers localised beta radiation to relieve severe pain from bone metastases in prostate, breast, and lung cancer, and osteosarcoma. Its half-life is 46.3 hours.
Is samarium a heavy or light rare earth element?
Samarium sits at the boundary conventionally used to divide light and heavy rare earth elements. With atomic number 62, it is typically grouped with the light rare earth elements (LREEs) alongside lanthanum, cerium, praseodymium, and neodymium, though some classification systems place it in an intermediate group. Its primary commercial product — samarium oxide — is extracted alongside other light REEs from bastnäsite and monazite.
