Take two neodymium earth magnets and place one in each hand. Each magnet might be about the size of a dime. Grab each magnet between your thumb and index finger and squeeze them tight. Now slowly bring your hands together. As your hands come closer to each other, you will begin to feel something pulling them closer to each other. When your hands and the neodymium magnets are about 6 inches apart, the force will start to intensify. Bring them just a little bit closer together and the magnets will "jump" from your hands and stick to each other. You will have a very difficult time trying to pull them apart.
That is the power behind these magnets that were discovered about 40 years ago in the 1970s. There are actually two types of rare earth magnets. The first rare earth magnet was made of an alloy of samarium and cobalt and hence the name samarium-cobalt magnet. A few years after scientists perfected the samarium-cobalt magnet, they began working on today's most powerful and popular permanent magnet, the neodymium magnet.
The neodymium magnet has certain attributes that cannot be found in any other permanent magnet. Ounce for ounce or pound for pound the combination of neodymium, iron and boron gives this magnet more remanence or strength through the magnetic field. As a comparison, an NdFeB magnet has a remnance of up to 1.4 while a ferrite magnet is rated with a remanence of .2 or about 1/7 the power of the neodymium magnet. Stated another way, you would need a ferrite magnet 7 times the size and weight of a neodymium magnet to have roughly the same strength.
As you can see, the incredible power of these magnets allows them to be made very small and still be very useful in numerous types of applications. When you pick up a battery powered drill or other portable power tool, chances are very good that a neodymium battery helps power that tool. Stereo speakers and headphones also rely heavily on these permanent powerful magnets. Other applications include use in computer hard drives and as the source of power in flashlights that you shake to illuminate.
Some of the different styles of neodymium earth magnets include those shaped like discs, cylinders or rings.
The disc is by far the most common rare earth magnet and is used for holding two surfaces together (closure) and for keeping metal display signs in place in or on retail store fixtures. There are many other applications, limited only by one's imagination.
The rare earth cylinder or rod-shaped magnet is taller than their diameter and they are sometimes used as a stud finder.
Ring earth magnets are shaped like a metal washer. A circular ring with a hole in the center, they are often encased in a metal holder and they make excellent magnets for metallic hooks.
Finally, when working with neodymium earth magnets, you need to take care not to get your fingers pinched between two magnets because the pain can be intense. With the larger earth magnets, there have been more than a few cases where people have had bones in their hands and even their arms snapped by the amazingly powerful magnets. These magnets are not toys and should be kept away from small children.
By combining boron, iron, some trace metals and neodymium the neodymium magnet is made. Similar to the metallic look and small but strong, this magnet can be shaped as blocks, discs or rings. Its most common use is in the computers but it can also be found in the speakers, printers, vehicle starters, linear actuators, microphones, servomotors, among many others.
When magnetic properties are required then neodymium proves to be a perfect choice for several reasons. If the requirement is about resisting demagnetization then this combination of metal proves just right. Even in ambient temperatures it performs perfectly well and carries a higher level of energy. Compared to different types of metals used for magnet purpose neodymium is an inexpensive material.
At the same time there are some negative points to the neodymium magnets. Because it is prone to corrosive effects, to assure a longer duration for the output some kind of coating is recommended. While at present its resistance to high heat is not very effective, scientists are at work to overcome this shortcoming. While using neodymium magnets there are some other things that requires being careful about. For example, it is not a perfect choice for magnet material to be used in traditional machining processes because the metal is prone to cracking and chipping. While on the other hand a big amount of coolant makes it ground abrasive. Incidence of fractures resulting from the heat can be decreased by this cooling process. Fire may be caused during the grinding process by the oxidized dust, but this risk is reduced by using the coolant.
For those looking for an inexpensive magnet there are other options, actually less costly than neodymium. The name is ceramic. Generally used for the speaker, ceramic magnets are also incorporated in the manufacturing of MRI (Magnetic Resonance Imaging) machines, outboard motor magnetos, lawnmower, automobile motors and assembling systems that are designed to retrieve, separate, hold and lift produced items. A diamond cutter or a grinding wheel is required for ceramic magnets during the finishing process. Shape variation is not that much possible with this magnet but it releases less energy compared to the neodymium magnets.
Compared to the neodymium magnets and ceramic, cobalt magnets are more costly. The higher price is because of the fact that against the demagnetization, cobalt is highly resistant, for a longer period maintains its temperature and higher amount of energy is released comparatively. The use of cobalt magnets are in wave tubes, linear actuators, satellites, computer hard disk drives, sensors, among many others. Cobalt magnets are also used when temporary stability is needed in any motor.
For a variety of uses alnico magnets are used. The usage include ringers for bells, security systems, loudspeakers, generators, microphones, telephones, magnetos, separators, motors, sensors, electron tubes, bearings, clutches, coin slots and radar. When it involves high level of heat then compared to neodymium magnets, alnico is better placed and can work at almost 1000 degrees Fahrenheit.
