RARE EARTH MAGNETS MRE
INTRODUCTION
Research to produce higher magnetic energy product (Bhmax) magnets than available with existing metal alloy and ferrite technology has resulted in the family of magnets known as rare earth magnets. Rare earth magnets cover many combinations of alloys, Samarium Cobalt (SmCo) and Neodynium Iron Boron (NdFeB) being the two groups which have been developed commercially. All commercial rare earth magnets are extremely brittle and break or crack easily. They should, therefore, be handled with care. Most rare earth magnets are magnetized through the thickness "T".
NEODYNIUM IRON BORON
NdFeB magnets have the highest energy per unit volume of any commercial magnet material with a Bhmax up to 45MGO. These magnets have a low maximum working temperature of 80/100 degrees Celsius, although higher temperature grades are now available at a premium cost. NdFeB magnets rust easily so they are normally supplied plated. Most shapes are pressed so there are a fixed number of disc and rectangular sizes. Special sizes, in small quantities can be produced economically.
DISC
Size = Diameter (D) x Thickness (T) mm
Magnetized T
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3 x 1 |
3 x 1.5 |
3 x 3 |
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4 x 1.5 |
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5 x 1.5 |
5 x 3 |
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6 x 1.5 |
6 x 4 |
6.5 x 5 |
6 x 25 |
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8 x 1.5 |
8 x 3 |
8 x 4 |
8 x 5 |
8x7xR0.5x1 |
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9 x 2 |
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10 x 1.5 |
10 x 3 |
10 x 5 |
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12 x 1.5 |
12 x 3 |
12 x 7 |
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13 x 7* |
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15 x 3 |
15 x 5 |
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18 x 7 |
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20 x 5 |
20 x 10 |
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22 x 5 |
22 x 10 |
22 x 20 |
22 x 25.4 |
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25 x 3 |
25 x 5 |
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30 x 5 |
30 x 3 |
30 x 25.4 |
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35 x 20 |
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44 x 6 |
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*unplated
RING
Size = Outside Diameter (OD) x
Inside Diameter (ID) x
Thickness (T) mm
Magnetized T
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5 |
2 |
3 |
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12 |
3.5 |
7 |
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15 |
5 |
5 |
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18 |
3.5 |
7 |
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20 |
5 |
5 |
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22 |
9 |
10 |
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24 |
18 |
4 |
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30 |
5 |
5 |
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32 |
18 |
4 |
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36 |
18 |
5 |
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50 |
12 |
8 |
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76 |
24 |
6 |
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RECTANGULAR
Size = Length (L) x Width (W) x Thickness (T) mm
Magnetized T
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50 |
50 |
20 N3 5M |
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50 |
20 |
8 |
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50 |
10 |
10 |
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40 |
8 |
4 |
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25 |
25 |
10 |
| 20 | 10 | 5 |
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19 |
8 |
8 |
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15 |
9 |
5 |
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10 |
10 |
50** |
* unplated
**magnetized through L
+N35M
SAMARIUM COBALT
The energy levels of SmCo magnets are in the region of 16/22MGO, being considerably lower than NdFeB magnets, but SmCo magnets have a higher working temperature and they do not rust. SmCo magnets are more expensive than NdFeB magnets and because of the cost premium we only carry limited sizes in stock.
BONDED RARE EARTH HIGH ENERGY MATERIALS
These newly developed materials comprise NdFeB magnet suspended in either a polymer or plastic. Bonded material has the advantage of mechanical strength, sometimes flexibility, and the ability to be easily shaped or fabricated. Whilst the energy levels are less than virgin material, with good design acceptably high energy magnet circuits can be produced. Bonded rare earth magnets are isotropic so multiple poles can be produced.