U.S. Permanent-Magnet Supply Concentration and the Strategic Potential of Sm–Fe–N: Element-Level Exposure, Bonded-Magnet Substitution, and High-Performance Research Targets

Abstract

The United States depends on internationally concentrated supply chains for permanent magnets, but trade statistics rarely distinguish the critical-element content of individual magnet chemistries. We combine U.S. import records for 2015–2025, exporter-reported mirror data, stage-specific rare-earth supply estimates, manufacturer magnetic-property data, and a 20,000-draw Monte Carlo model to assess the strategic opportunities offered by samarium–iron–nitrogen (Sm–Fe–N) magnets. China’s share of U.S. metal-magnet import value increased from 64.7% in 2015 to 72.7% in 2025, after reaching 79.8% in 2023; the estimated trend was 1.54 percentage points per year (95% confidence interval 0.78–2.30). Customs code HS 8505.11 combines several magnet chemistries, so these figures describe supplier concentration for loose metal magnets rather than Sm–Fe–N-specific trade. At equal nominal magnetic energy, commercial bonded Sm–Fe–N requires a median 0.72 times the volume of bonded NdFeB and reduces total rare-earth mass by 146 g per kilogram of incumbent magnet replaced, while eliminating 266 g of Nd and Pr. These gains coexist with an important exposure trade-off: samarium is itself subject to Chinese export controls. A simplified demagnetization model indicates that binder ratings often limit commercial bonded Sm–Fe–N before the modeled magnetic working-point limit, conditional on adequate demagnetization-curve squareness. A separate, explicitly prospective analysis identifies dense anisotropic Sm–Fe–N with an energy product near 300 kJ/m³ and room-temperature intrinsic coercivity of approximately 0.79–1.18 MA/m as a target for high-temperature traction-motor applications; this is not a demonstrated bulk magnet. Estimated samarium contained in current global mine output could theoretically support approximately 29.3 kt/year of bonded Sm–Fe–N, subject to recovery, separation, processing and competing demand. Together, the results identify demonstrated opportunities in bonded magnets and quantify research targets for expanding the role of Sm–Fe–N in supply-chain diversification.