Rare earth magnets are manufactured from various metals and formed into an alloy. These magnets were first made in 1970s and are still ruling the world as the strongest magnets available for use. They are three times stronger than the ceramic and ferrite magnets as far as their magnetic field is concerned. However, they are brittle, weak and can corrode easily. Moreover, they are plated and coated so as to avoid them from chipping or breaking.
Strength Factor
It is generally believed that these magnets are precious as they are very rarely available, which is not true. They are as cheap as tin or lead. Their strength was realized in 1966 when two of the US air Force scientists discovered their potential in a test. Elements of lanthanide series are easy to magnetize as they possess ferromagnetic properties. When these elements are in their pure form, they exhibit magnetic properties but at low temperatures. To enhance their ability to retain magnetism at higher temperatures than normal, these magnetic materials are mixed with iron, nickel and cobalt. Thus, they become more useful at elevated temperatures, which is generally requires when they are used in industries.
Neodymium
Created in 1980s, neodymium magnets are still the strongest and cheapest of all lanthanide magnets available. Iron, boron and neodymium is alloyed together to create a strong magnet. Neodymium magnets are used in various applications such as in audio devices and computer hard drives. These magnets are covered with a coating of another strong metal to prevent corrosion and decay to their surface. The protective covering on neodymium magnets can be of metals like gold, zinc, nickel, tin or even epoxy resin. Initial neodymium magnets were expensive and were only used for special applications. However, in the past 20 years or so, neodymium magnets have become cheap and readily available to the general public. Because of its low cost, neodymium is also being used in toys that are made for children.
There are some disadvantages of these magnets as well. As these magnets are very strong, physical injury can happen to a person that accidently comes between two of these magnets. The injury can be more severe depending on the size of the magnet. Bone fracture can also happen when handling two large sized magnets. The force of attraction of these magnets is directly proportional to their size and mass, which can be fatal for people in the vicinity as they can shatter with sprinkles spreading in high velocities in all directions. Moreover, when these magnets come in contact with other magnetic materials, they can be damaging. Credit cards, mobile phones and other electronic items should be kep away from their vicinity to avoid any damage.
The diminutive size of rare earth magnets contradict their fantastic strength; by comparison they demonstrate anywhere from five to fifteen times the magnetic strength, or energy, of a common household magnet such as those displayed on most residential refrigerators. The most commonly known and utilized of all rare earth magnets are Samarium Cobalt and Neodymium-Iron-Boron.
The 'titan' of them all:
Neodymium-Iron-Boron is currently recognized as the strongest of all known rare earth magnets. As with all great titans, even this rare earth has its failings, Neodymium-Iron-Boron is very sensitive to extreme heats, exposure to temperature ranges over 150 degrees Celsius will result in decreased magnetic strength, whereas Samarium Cobalt will increase in registered strength.
Strength Affecting Factors:
Environmental conditions are key factors in the magnetization of any metal; heat, for instance, affects all metals, to different degrees. Radiation also play a substantial factor in the overall magnetic property of any metal. The presence of a strong electrical current can also affect magnetic properties, either in a contributory or detracting fashion, all dependent on the type of metal.
Close proximity to another magnet may also negatively affect the pull of a magnet. Neodymium-Iron-Boron and other Neo metals, are known to corrode quickly in more humid environments. To combat this many manufacturers have begun incorporating a plastic or rubberized coating to their magnets. While vibration or physical shocks, such as from being dropped generally has no noticed affect on magnetic properties, it can damage the metal itself.
Strength of pull:
Magnetic pull will decrease as the distance between the affected object and the magnet increase. That is to say that if you were to hold a metal object a few inches from a magnet the magnetic pull would be, by far, stronger than if you were to hold it several feet away. It is also key to note that all rare earth magnets, demonstrate their own force-to-distance ratios, again this is a result of the different types of metals.
Loss of magnetization:
Materials can magnetized and demagnetized at will. Providing that the metal has not been adversely affected by exposure to extreme heat, restoring its original magnetic strength is a fairly simple process. Many companies will demagnetize a large magnet when placing it into storage and then re-magnetize it when they return it to use or service.
Gauging Strength:
Magnetic strength is measured by various devices such as pull-testers, magnetometers, and gaussmeters. The Gaussmeter and Magnetometer utilize degrees of measurement known as Gauss. The Pull-Testers utilize various arbitrary units of measure ranging from kilograms, pounds, foot-pounds and so forth that are more easily interpreted. These units range in average cost from approximately $400 to several thousand dollars.
Polarity:
The standard industrial definition states that the North Pole of a magnet will seek out the North Pole of the Earth when allowed to freely rotate. Comparatively, the South Pole of a magnet shall seek out the South Pole of the Earth. Many traditional navigational tools have employed magnets in order to determine direction of travel and assist in the plotting of course of travel.
A word to the wise:
Due to their intense strength, Rare Earth Magnets should be handled with care and caution so as not to damage them; avoid allowing the to freely slam into an attracted metal as this may contribute to cracking. It is also wise to remember that almost all electronic devices are affected by magnetic fields and can be easily damaged by prolonged exposure, and the magnetic strips on the back of most credit cards, key cards, or other related products can be erased the same as the hard drive on most computers by exposure to strong magnetic fields.
