Rare Earth Magnets

History– Loadstones (Fe3O4)– Steels– Alnicos (Al, Ni, Co, and Fe)– Ferrites– Rare-Earth

• Samarium-Cobalt• Neodymium-Iron-Boron

What Makes a Magnet• Quantum Level

• Spinning and Orbiting Electrons

• Hysteresis Loop• Crystal Structure

– Tetragonal Symmetry

• Rare-Earth Element– High Curie

Temperature

– High Magnetization

– High Coercivity

– High Remanence

Processing Rare-Earth Magnets• Classifications

– Bonded• Compressing a mixture of NdFeB alloy flakes with a resin

bonding agent

– Sintered• Powdered alloy (3-5 micrometers) is aligned in an

electromagnetic coil, pressed into shape, and then sintered at 1000 degrees Celsius

• High Corrosion Factor– Types of coatings

• Aluminum ion deposition• Nickel plating• Epoxy-resin Painting• Electrolytic Deposition

Applications of Rare-Earth Magnets

• Aerospace– Frictionless Couplings

– Auto Compass

• Automotive

• Medical– Magnetic Resonance Imaging

– Dentures

– Wound Closures

– Optical Implants

• Domestic– Head sets

– Electric Clocks

– Hearing Aids

• Electronic Instrumentation– Sensors

– Servo Motors (robotics)