Magnetic Properties
Some important properties used to compare permanent magnets are: remanence (Br), which measures the strength of the magnetic field; coercivity (Hci), the material's resistance to becoming demagnetized; energy product (BHmax), the density of magnetic energy; and Curie temperature (Tc), the temperature at which the material loses its magnetism. Rare earth magnets have higher remanence, much higher coercivity and energy product, but (for neodymium) lower Curie temperature than other types. The table below compares the magnetic performance of the two types of rare earth magnet, neodymium (Nd2Fe14B) and samarium-cobalt (SmCo5), with other types of permanent magnets.
| Magnet | Br (T) | Hci (kA/m) | (BH)max (kJ/m3) | Tc (°C) |
|---|---|---|---|---|
| Nd2Fe14B (sintered) | 1.0–1.4 | 750–2000 | 200–440 | 310–400 |
| Nd2Fe14B (bonded) | 0.6–0.7 | 600–1200 | 60–100 | 310–400 |
| SmCo5 (sintered) | 0.8–1.1 | 600–2000 | 120–200 | 720 |
| Sm(Co,Fe,Cu,Zr)7 (sintered) | 0.9–1.15 | 450–1300 | 150–240 | 800 |
| Alnico (sintered) | 0.6–1.4 | 275 | 10–88 | 700–860 |
| Sr-ferrite (sintered) | 0.2–0.4 | 100–300 | 10–40 | 450 |
Read more about this topic: Rare-earth Magnet
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