Why rare earth and neodymium magnets are preferred over the other types of magnets?
Rare earth magnets are one of the strongest magnets which are commercially available on earth and as a type of it, neodymium magnets are also useful in many purposes, so much so that it is generally believed that earth’s technology would have been a good two or three decades behind of this magnet wasn’t invented. So let’s check how and why this type of magnet is better than others:
- Ceramic magnets:
- Relative strength: The strength of a magnet’s magnetic field is measured with BHmax, so the higher the BHmax, the more powerful the magnet. Ceramic magnets contain a BHmax of 3.5 whereas the two rare earth types called samarium cobalt contains a BHmax of 25 and Neodymium contains a BHmax of 40. So ceramic magnets are around 10 times weaker than permanent magnets. Also because of its strength, handing permanent magnets over 2″ required caution.
- Relative resistance to thermal stress: It should be noted that magnets tend to lose their strength and other properties when heated above their Tcurie temperature. Ceramic magnets have a Tcurie of 460 degree Celsius whereas samarium and neodymium have a Tcurie of 750 and 310 respectively. But if they are cooled below their top temperature, called Tmax, then they can regain their properties. So in lieu of this, ceramic magnets have a Tmax of 300 degree Celsius whereas samarium cobalt and neodymium magnets have a Tmax of 150 degree Celsius.
- Relative durability: Neodymium magnets are brittle and as a result are difficult to use. On top of this, it also corrodes easily. SmCo or samarium cobalt magnets are slightly less brittle and are also corrosion resistant. Ceramic magnets provide good resistance to both corrosions as well as demagnetization.
- Cost: Ceramic magnets are less costly than both SmCo and NdFeB (neodymium) magnets.
So these two magnets are used in different applications. Like ceramic magnets are used in fridges or in stereos whereas rare earth and neodymium magnets are used in generators, levitation machines, jewellery, hard disk drives, motors and more. Both of them are useful in their own unique way and so these above properties should be kept in mind while choosing which magnet to go for.