Rare-earth magnet facts for kids
Rare-earth magnets are strong permanent magnets made from alloys of rare earth elements.
Developed in the 1970s and '80s, rare-earth magnets are the strongest type of permanent magnets made. They have much stronger magnetic fields than other types such as ferrite or alnico magnets.
There are two types: neodymium magnets and samarium-cobalt magnets. Some rare-earth magnets such as Terfenol-D are magnetostrictive. They also have uses e.g. in speakers.
Rare earth magnets are extremely brittle and also vulnerable to corrosion, so they are usually plated or coated to protect them from breaking, chipping, or crumbling into powder.
Applications
Since their prices became competitive in the 1990s, neodymium magnets have been replacing Alnico and ferrite magnets in the many applications in modern technology requiring powerful magnets. Their greater strength allows smaller and lighter magnets to be used for a given application.
Common applications
Common applications of rare-earth magnets include:
- computer hard disk drives
- wind turbine generators
- speakers / headphones
- bicycle dynamos
- MRI scanners
- fishing reel brakes
- permanent magnet motors in cordless tools
- high-performance AC servo motors
- traction motors and integrated starter-generators in hybrid and electric vehicles
- mechanically powered flashlights, employing rare earth magnets for generating electricity in a shaking motion or rotating (hand-crank-powered) motion
- industrial uses such as maintaining product purity, equipment protection, and quality control
- capture of fine metallic particles in lubricating oils (crankcases of internal combustion engines, also gearboxes and differentials), so as to keep said particles out of circulation, thereby rendering them unable to cause abrasive wear of moving machine parts
Other applications
Other applications of rare-earth magnets include:
- Linear motors (used in maglev trains, etc.)
- Stop motion animation: as tie-downs when the use of traditional screw and nut tie-downs is impractical.
- Diamagnetic levitation experimentation, the study of magnetic field dynamics and superconductor levitation.
- Electrodynamic bearings
- Launched roller coaster technology found on roller coaster and other thrill rides.
- LED Throwies, small LEDs attached to a button cell battery and a small rare earth magnet, used as a form of non-destructive graffiti and temporary public art.
- Neodymium magnet toys
- Electric guitar pickups
- Miniature figures, for which rare-earth magnets have gained popularity in the miniatures gaming community for their small size and relative strength assisting in basing and swapping weapons between models.
Images for kids
-
Neodymium magnets (small cylinders) lifting steel balls. As shown here, rare-earth magnets can easily lift thousands of times their own weight.
-
Neodymium magnet with nickel plating mostly removed
See also
In Spanish: Imán de tierras raras para niños
