Rare Earth Magnets

Rare-earth magnets fall under the category of permanent magnets having a composition of alloys manufactured from rare earth element(mostly elements from lanthanide series, and  alloys. They were developed in the year 1970s and 1980s and they are the strongest type of permanent magnets. They produce magnetic fields that are quite strong than other types of magnets like alnico and ferrite magnets.  The rare earth magnets have a field strength of more than 1.4 tesla, whereas ceramic and ferrite magnets have fields of 0.5 to 1.0 Tesla.  Some other types of magnetostrictive rare earth magnets such as the Terfenol-D find applications in the audio systems.

Rare are earth magnets tend to be highly fragile and also would be exposed to corrosion, so they would be typically coated or plated to protect them from breaking or crumbling into powder.

The term “rare earth” could be confusing as these metals are not particularly rare or precious; they are usually abundant in plenty like tin or lead.

Types of Rare Earth Magnets:

There are two types of rare earth magnets:

  • Samarium-cobalt
  • Neodymium

Samarium-cobalt Magnets: 

  • These are the first group of rare earth magnets discovered are used less unlike neodymium magnets owing to their cost being higher and magnetic field strength being weaker.
  • The samarium-cobalt has a Curie temperature being higher and has a higher resistance to oxidation, but sintered samarium-cobalt magnets are fragile and vulnerable to chipping and cracking, and might crumble when exposed to thermal shock.

Neodymium Magnets:

  • These type of magnets were discovered during the 1980s and are the most affordable and strongest type of rare-earth magnet. They are manufactured out of an alloy of iron, neodymium and boron, termed by the abbreviation NIB.
  • Neodymium magnets have a higher coercivity. They are of use in various applications such as electric motors for jewellery clasps, hard disk drives and magnetic hold-downs.

Uses of Rare Earth Magnets:

Common Applications:  Rare-Earth Magnets has some common applications like:

  • Bicycle dynamos
  • Permanent magnet motors present in cordless tools
  • Magnetic resonance imaging devices
  • Audio headphones
  • High-performance AC servo motors
  • Computer hard disk drives
  • Industrial uses such as maintaining product purity, equipment protection, and quality control
  • Wind turbine generators
  • Integrated starter-generators and traction motors generators in electric vehicles
  • Fishing reel brakes.

Other Applications: Rare-earth magnets have other applications like:

  • LED Throwies
  • Launched roller coaster
  • Electrodynamic bearings
  • Linear motors(used in magnetic levitation trains)
  • Electric guitar pickups
  • Stop motion animation
  • Diamagnetic levitation experimentation – It is the study of the superconductor dynamics and magnetic field levitation
  • Neodymium magnet toys

Stay tuned with BYJU’S to learn more about magnets, magnetic poles and much more.

Practise This Question

When two charged glass rods, after being rubbed with silk cloths are brought towards each other, they: