Rare earth magnets are basically permanent strong magnets which are made of an alloy of different rare earth elements. The Rare earth magnets were developed in the year of 1970 and it is one of the strongest types of magnets which are permanent. The rare earth magnets have a very strong magnetic field than the other magnets such as alnico and ferrite. The magnetic field that is produced by all the rare earth magnets has a strength of 1.4 teslas whereas the other magnets have a strength of about 0.5 teslas.
There are basically two types of magnets
• Neodymium Magnets
• Samarium Cobalt Magnets
Rare earth magnets such as Terfenol-D are very often used in all the loudspeakers. Rare earth magnets are all very much vulnerable to corrosion and they are also very brittle in nature. All the rare earth magnets are either coated or plated into things so that they don’t break or become powder.
The rare earth magnets were discovered by G. Hoffer and K.J. Strnat at the United States Air Force Materials Laboratory. The materials used in rare earth magnets are not rare at all so at times the name could be misleading.
All the rare earth magnets elements are ferromagnetic which means that the elements are more or less like iron and can be magnetized so that they become permanent magnets. The Curie temperature of all the Ferro magnets is below the temperature of a room. When the Ferromagnets are in pure form, the magnetism of the elements is in low temperature. The Ferro magnets easily form different compounds with help of transition metals like cobalt, nickel, and iron. Generally, the rare earth magnets are made of iron, nickel, and cobalt.
Reason for the strength of rare earth magnets:
• The crystalline structure which has a very high magnetic anisotropy
• All the atoms of the rare earth magnet elements have high magnetic moments because of the unpaired electrons on the outer orbits
The crystals of all the materials of rare earth magnets magnetize itself with crystal axis. All the rare earth magnets are made of microcrystalline grains which are all aligned in a magnetic field during its manufacture to keep all the magnetic axes in the same direction. The result of the incomplete f-shell makes the element more magnetic in nature. Basically, all the unpaired electrons on the outer most shell create the magnetic field of the element.
Properties of Permanent Magnets
• Energy product
• Curie Temperature
Remanence: This basically helps in measuring the strength of the magnetic field
Coercivity: The resistance of the material to become demagnetized
Energy Product: The basic density of the energy which is magnetic
Curie temperature: The exact temperature where the material loses its magnetic properties
Application of rare earth magnets
Rare earth magnets are used in a lot of places where they are either coated or plated on some material. Basically, rare earth magnets are used in all kinds of hard drives which are been used in computers. Rare earth magnets are also used in different wind turbine generators and are different audio devices like headphones and speakers. The rare earth magnets are used in devices which work on magnetic resonance imaging and they are also used in different bicycle dynamos. All the cordless tools generally use rare earth magnets.
The rare earth magnets are also often used in different linear motors which are popular in mag lev trains. All the electro dynamic bearings use rare earth magnets very often. Electric guitar pickups are generally coated with rare earth magnets to create a magnetic field in the instrument.
Right now there is work going on in the United States of America for finding out a substitute for rare earth magnets. The whole search is sponsored by ARPA-E which is also known as The Advanced Research Projects Agency-Energy. All this research has been boosted because all the rare earth magnets were being exported from China earlier and since the new export lays of China all the countries are more eager to make their own substitute of rare earth magnets. China is the best place to find all the minerals of a rare earth magnet right now.