Whether you are buying magnets for home, office, hobby, or industrial use, you surely want to protect your new purchase to ensure they last as long as possible and stay as strong as the day you bought them. Each type, material, shape and size of magnet will have a different durability level, but optimal care will prolong the life of all modern permanent magnets. These are the 4 most common reasons magnets start to lose their charges.
1. They Get Old
While the passage of time does weaken the strength of a magnet, the changes are very slow. So much so that even over the whole of the time you possess any magnet, the release of charge is not likely to be very noticeable. All other factors will have a greater total effect on the magnet, and assuming you properly store and care for your magnets, they will last a very long time.
2. They Get Very Cold (Or Hot)
Temperature variation can cause magnets to lose some or all of their magnetic charge. Depending on how extreme the temperature, these losses can be temporary or permanent.
Magnets exposed to temperatures not outside their reversible operating temperatures may temporarily lose strength while heated, but will regain this force once brought back to optimal temperature. This data is different for every type and material, and should always be available when purchasing your magnet. More permanent damage that is only reversible by re-magnetization will occur when the magnet is exposed to temperatures above this point.
While a magnet will regain most or all of the losses caused by heating to below its maximum use temperature, heating above this point causes permanent loss of magnetic charge that cannot be reversed.
3. Reluctance Changes
When the operating slope of a magnet is modified, the variance can cause a shift in magnetic charge. This can be brought on by displacement from a circuit, such as taking out an operating magnet or placing on in a circuit, or by changing the magnet properties while it is in use. The level of magnetic charge that is reduced by this depends upon how extreme the alterations are and the type and properties of the magnet.
4. External Charges
Magnets that are not protected from outside magnetic fields may fall prey to loss of magnetic charge. Certain magnets are more susceptible to this effect, such as Alnico. External magnetic fields that may lead to demagnetization are encountered multiple ways, environmentally and through improper storage. Environmental factors can include items like electromagnets and coils nearby. Storage of magnets near each other, particularly with opposing forces too close, can also cause loss of magnetic charge.
Magnets are typically resistant to traumas causing shock or vibration, and will not lose magnetic strength when exposed to them. The exception to this is traumas that cause damage to the structure of the magnet. Cracks, chipping, breaking and erosion all equal a decrease in the mass of the magnetized material, and reduction in force. Proper handling and storage are therefore critical to the long life of your magnets.
Occasionally -most often in industrial usage- radiation becomes a concern in the preservation of magnetic charge. If the use you envision for your magnets includes exposure to moderate or high levels or radiation, this should be discussed as an early consideration.
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