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Material World
Element · Sm

Samarium

The rare earth behind the magnets that work when neodymium ones fail.

Samarium is a moderately hard rare earth with an unusual claim: samarium-cobalt was the first commercially important rare-earth permanent magnet, predating the neodymium magnets that later displaced it in most applications.

It was not displaced everywhere, and the reason is temperature. Samarium-cobalt magnets keep their strength at temperatures that demagnetise neodymium ones, and they resist corrosion far better. Where the environment is hot or hostile, samarium remains the choice despite costing more.

Uses

Samarium-cobalt magnets are used in aerospace and military hardware, in high-temperature motors and generators, in travelling wave tubes for satellite communications, and in precision instruments where the magnet's strength must not drift with temperature.

Samarium is also a strong neutron absorber, used in reactor control rods. Samarium-153 is used in nuclear medicine to relieve pain from bone cancers, and samarium compounds catalyse certain organic reactions, notably as samarium diiodide, a widely used single-electron reducing agent.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is used as

  • Permanent magnets — application · samarium-cobalt keeps its strength where neodymium magnets fail

is produced by

  • Rare earth separation — process · a light rare earth, separated from its neighbours by countercurrent solvent extraction

is an alternative to

  • Neodymium — element · in permanent magnets: samarium-cobalt is weaker than neodymium-iron-boron and holds its magnetism far better when hot, so it keeps the applications where temperature rather than strength is the constraint

is a component of

  • Samarium–cobalt magnet — alloy · 20–35% · the rare earth that supplies the anisotropy, and essentially the only large use samarium has

Sources

  • Material World
    Our own writing
  • Wikidata
    Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
  • PubChem
    US National Library of Medicine · Mixed — aggregated third-party content, rights retained by depositors
  • NIST — National Institute of Standards and Technology
    United States Department of Commerce · US Government work — public information, credit requested

Questions this page answers

Where it comes from, and what it becomes

Follow Samarium back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

  • Samarium → is produced by (a light rare earth, separated from its neighbours by countercurrent solvent extraction) → Rare earth separation → takes as input (the principal ore of the light rare earths, carrying all of them together) → Bastnäsite
  • Samarium → is produced by (a light rare earth, separated from its neighbours by countercurrent solvent extraction) → Rare earth separation → takes as input (the other feed alongside bastnäsite, bringing thorium into the residues with it) → Monazite
  • Samarium → is produced by (a light rare earth, separated from its neighbours by countercurrent solvent extraction) → Rare earth separation → takes as input (the heavy rare earth feed, where monazite and bastnäsite bring the light ones) → Xenotime

Downstream — what it becomes

  • Samarium → is a component of (the rare earth that supplies the anisotropy, and essentially the only large use samarium has) → Samarium–cobalt magnet → is used as (weaker and untroubled by heat, which keeps it where temperature rather than strength is the constraint) → Permanent magnets
  • Samarium → is used as (samarium-cobalt keeps its strength where neodymium magnets fail) → Permanent magnets