Rare-earth Magnets

Rare-earth magnets have unique properties that make them essential in many advanced applications. Here are their key characteristics:

High Magnetic Strength

• They produce extremely strong magnetic fields (higher than ferrite or alnico magnets).
• Neodymium magnets can have a magnetic field strength (Br) of up to 1.4 Tesla.

High Coercivity (Resistance to Demagnetization)

• Rare-earth magnets retain their magnetism even when exposed to external magnetic fields.
• Samarium-cobalt magnets have higher coercivity, making them ideal for high-temperature environments.

High Energy Density

• Their high energy product (BHmax) allows for strong magnetic fields in small sizes, making them ideal for compact devices.

Brittle and Hard

• These magnets are brittle and prone to chipping or breaking under mechanical stress.
• They often require protective coatings like nickel, gold, or epoxy.

Temperature Sensitivity

• Neodymium magnets lose magnetism at high temperatures (~80–200°C, depending on the grade).
• Samarium-cobalt magnets have a higher Curie temperature (up to 800°C), making them better for high-heat applications.

Corrosion Susceptibility

• Neodymium magnets are prone to oxidation and rust, requiring coatings or protective layers.
• Samarium-cobalt magnets are naturally more corrosion-resistant.

Anisotropic Magnetization

• These magnets are anisotropic, meaning they have a preferred direction of magnetization, which makes them more efficient.