Samarium cobalt magnets were the original high-performance permanent magnet — the technology that made precision-guided missiles, satellite attitude control, and miniaturized radar possible during the 1970s and 1980s. Then neodymium-iron-boron magnets arrived in 1984, offered stronger fields at lower cost, and samarium cobalt was demoted to a niche material for applications where NdFeB couldn’t survive: environments above 300°C, corrosive atmospheres, radiation exposure, and systems where demagnetization from temperature cycling would be mission-fatal. Fighter jet engine accessories. Missile fin actuators. Traveling wave tubes in military radar. Naval sonar transducers. Satellite reaction wheels. The applications are small in volume and enormous in consequence. Samarium cobalt accounts for less than 2% of global permanent magnet production. It is irreplaceable in systems where failure means a missile doesn’t steer, a radar doesn’t function, or a submarine doesn’t hear. And as of April 4, 2025, China placed samarium — along with terbium, dysprosium, and four other rare earths — under export controls that have effectively halted the reliable flow of SmCo magnets to Western defense contractors.
What makes SmCo different
SmCo magnets come in two grades: SmCo5 (samarium-cobalt 1:5) and Sm₂Co₁₇ (samarium-cobalt 2:17). Both offer thermal stability that NdFeB cannot match. NdFeB magnets start losing their magnetic properties above 80°C without terbium or dysprosium additives, and even with additives, they max out around 200°C. SmCo magnets operate at 250-350°C with no additives and no performance degradation. They resist corrosion without the nickel-copper-nickel plating that NdFeB requires. They’re immune to radiation damage at levels that would demagnetize NdFeB. The tradeoff is energy density — NdFeB magnets produce stronger fields per unit volume — and cost, because both samarium and cobalt are expensive relative to neodymium and iron.
For commercial EV motors and wind turbines, NdFeB wins on performance per dollar. For a missile guidance system operating in an engine bay at 300°C where corrosion resistance matters and magnetic stability is non-negotiable, SmCo is the only option. That division of labor — NdFeB for the clean-energy economy, SmCo for the defense industrial base — is what makes the April 2025 export controls particularly consequential. The Battlefields of the Future course covers how modern weapons systems depend on precision components. SmCo magnets are among the most precision-critical and least substitutable of those components.
The supply chain that doesn’t exist outside China
China refines approximately 90% of the world’s samarium. SmCo magnet manufacturing is concentrated in China because the entire rare earth separation and metal refining supply chain is concentrated in China. When Arnold Magnetic Technologies — one of the few Western SmCo manufacturers, with facilities in the United States, Switzerland, and Thailand — received the April 4 export control announcement, their Chief Commercial Officer noted they had already secured more than a year’s worth of samarium metal inventory. Arnold has since built a non-Chinese samarium and cobalt supply chain to feed its Swiss and Thai manufacturing. That makes Arnold an exception. Most Western magnet buyers are not exceptions.
The Western alternatives that exist are narrower than the headlines suggest. Lynas Rare Earths announced in March 2026 that it had produced the first separated samarium oxide at its Malaysian facility — the first non-Chinese samarium separation in commercial history. The milestone is genuine but the scale is small. Solvay holds a legacy stockpile of roughly 200 tonnes of samarium nitrate in France — material that is finite, already spoken for by defense programs, and not a flowing supply. The Samarium Magnet Company, a Saudi Arabia-based manufacturer, has positioned itself as a non-Chinese alternative with Gulf-region and African rare earth sourcing — but it is a single facility serving a global demand that Chinese producers had supplied for decades. Energy Fuels in Colorado is exploring rare earth separation using uranium processing infrastructure, but is not producing samarium at commercial scale.
The NDAA Section 870 deadline compounds the pressure. Effective January 1, 2027, the U.S. Department of Defense will prohibit the acquisition of samarium cobalt and NdFeB magnets that are mined, refined, melted, or produced in China, Russia, Iran, or North Korea. Defense contractors who have been purchasing Chinese-origin SmCo magnets — which, until April 2025, was the only way to purchase SmCo magnets in meaningful volume — have roughly eight months from this writing to secure NDAA-compliant supply chains. Arnold has one. Lynas has started producing samarium oxide. Everyone else is scrambling.
The April 2025 controls in practice
The export control process has been worse than the export control announcement. MOFCOM’s April 2025 Announcement No. 18 required export licenses for samarium, SmCo magnets, and SmCo alloys. Provincial commerce bureaus initially communicated 45-60 day review windows. Actual processing times have exceeded those estimates consistently. By mid-2025, Arnold reported that “military-adjacent, aerospace, and sophisticated sensor programs almost never receive approvals.” Commercial applications face intense scrutiny of end-use declarations, and licenses are issued on a per-shipment basis — even identical repeat orders require separate license applications.
The practical consequence is that Western companies cannot plan production around Chinese SmCo supply. A magnet manufacturer outside China that had legally purchased samarium earlier in 2025 was contractually required to block shipment of finished SmCo ingots after the October controls expanded to cover Chinese-origin minerals used in dual-use applications — even though the alloy was manufactured and processed entirely outside China. The extraterritorial reach is the same mechanism the terbium post documented: China asserts licensing authority over products containing Chinese-origin rare earth inputs at concentrations as low as 0.1%, regardless of where the product is manufactured. The semiconductor supply chain has ASML’s export restrictions limiting Chinese access to EUV lithography. China’s rare earth export controls are the mirror image: limiting Western access to the materials that go inside the machines.
The cobalt complication adds a second layer of supply risk. Cobalt constitutes roughly 30% of SmCo alloy by mass, and cobalt supply is concentrated in the DRC, where artisanal mining, conflict, and price volatility create their own supply chain constraints. SmCo magnet manufacturers face simultaneous pressure on both inputs: samarium from Chinese export controls and cobalt from DRC supply instability. The intersection of those two constraints — one geopolitical, one geological — is what makes SmCo the most supply-constrained magnet technology in the world.
The comeback nobody wanted
The irony of samarium’s 2025-2026 resurgence is that nobody in the magnet industry wanted it. NdFeB was supposed to be the permanent magnet of the future — cheaper, stronger, increasingly available from non-Chinese sources as MP Materials and Lynas expanded light rare earth production. SmCo was the legacy technology, maintained for defense applications where nothing else would do but otherwise declining in commercial relevance. Then China put samarium, terbium, and dysprosium under export controls in the same announcement, and the magnet industry discovered that both its leading-edge technology (high-temperature NdFeB with terbium/dysprosium) and its legacy fallback (SmCo) were simultaneously supply-constrained by the same country’s export licensing regime. The diversification that was supposed to protect the supply chain — “we’ll use NdFeB for commercial and SmCo for defense” — turned out to be diversification within a single point of failure.
The gallium/germanium controls in 2023 restricted semiconductor feedstock. The antimony controls in 2024 restricted ammunition and flame retardant materials. The graphite controls in 2023 restricted battery anode materials. The April 2025 rare earth controls restricted the magnets that go into everything — EVs, wind turbines, guided missiles, radar, sonar, MRI machines, industrial robots, and the semiconductor lithography equipment that SmCo magnets sit inside. Each escalation in the sequence has targeted a higher-value, harder-to-substitute category of material. Samarium is the escalation that reached the defense industrial base.
This is the kind of supply chain our Rare Earth Elements course was built to map — where a magnet technology the West invented in the 1970s, let China monopolize in the 2000s, and assumed would always be available as a commodity, became in April 2025 the most restricted defense-critical material on the export control list, with eight months left before U.S. law prohibits the Pentagon from buying it from the only country that produces it at scale.
Leave a Reply