1. Composition and Materials
Neodymium Magnets (NdFeB): Made from an alloy of neodymium, iron, and boron.
Samarium-Cobalt Magnets (SmCo): Composed of samarium and cobalt, often with other elements like iron and copper.

2. Magnetic Strength
Neodymium Magnets: Known as the strongest type of permanent magnet available. They have high magnetic strength, with a maximum energy product (BHmax) ranging from 28 to 52 MGOe (Mega Gauss Oersteds).
Samarium-Cobalt Magnets: While not as strong as neodymium magnets, they still offer considerable magnetic strength, with a BHmax between 16 and 32 MGOe.

3. Temperature Stability
Neodymium Magnets: Performance can degrade at higher temperatures. They generally operate effectively up to 80-150°C, depending on the grade. Special high-temperature grades can withstand up to 200°C.
Samarium-Cobalt Magnets: Superior temperature stability compared to neodymium magnets, maintaining their magnetic properties at temperatures up to 300°C or higher.

4. Resistance to Corrosion
Neodymium Magnets: Susceptible to corrosion and often require protective coatings (nickel, zinc, epoxy) to prevent rust and degradation.
Samarium-Cobalt Magnets: Naturally more resistant to oxidation and corrosion, often used without additional coatings.

5. Cost and Availability
Neodymium Magnets: Generally more affordable due to more abundant raw materials and simpler manufacturing processes. However, prices can fluctuate based on supply chain and demand for rare earth elements.
Samarium-Cobalt Magnets: More expensive due to the rarity of samarium and the complex manufacturing process.

6. Mechanical Strength
Neodymium Magnets: Brittle and prone to chipping and cracking under mechanical stress. They require careful handling.
Samarium-Cobalt Magnets: Also brittle, but slightly more robust than neodymium magnets under mechanical stress.

7. Applications
Neodymium Magnets: Used in a wide range of applications due to their strength, including hard drives, electric motors, medical devices, and consumer electronics.
Samarium-Cobalt Magnets: Preferred in high-temperature applications such as aerospace, military, and automotive industries, where thermal stability and corrosion resistance are critical.