Some important properties of permanent magnets are: The remanence (B r), which measures the intensity of the magnetic field; the coercive force (H ci) is the resistance of the material to the demagnetization; energy product (BH max) is magnetic energy density; and Curie temperature (T C) is the temperature that the material loses magnetism.
Rare earth magnets have higher remanence, higher coercivity and energy product, but its Curie temperatures (for neodymium) are lower than other types. The next table compares the magnetic properties of two
rare earth magnets of neodymium.
|
Magnets
|
Br (T)
|
H ci (kA/m)
|
(BH) max (kJ/m 3)
|
|
Nd 2 Fe 14 B (sintering)
|
1.0-1.4
|
750-2000
|
200-440
|
|
Nd 2 Fe 14 B (Adhesion)
|
0.6-0.7
|
600-1200
|
60-100
|
|
SmCo 5 (sintering)
|
0.8-1.1
|
600-1200
|
120-200
|
|
Sm (Co,Fe,Cu,Zr) 7 (sintering)
|
0.9-1.15
|
450-1300
|
150-240
|
|
Al-Ni-Co alloy (sintering)
|
0.6-1.4
|
275
|
10-88
|
|
Sr ferrite(sintering)
|
0.2-0.4
|
100-300
|
10-40
|
