Provided that the material has not been damaged byextreme heat, the magnet can be re-magnetized back to its original strength.

For a circular magnet with a radiusof R and Length L, the field at the centerline of the magnet a distance X fromthe surface can be calculated by the following formula (where Br is theResidual Induction of the material):

The factors can affect a magnet’sstrength:Heat
Radiation
Strong electrical currents in closeproximity to the magnet
Other magnets in close proximity tothe magnet
 (Neo magnets will corrode in highhumidity environments unless they have a protective coating.)
 Shock and vibration do not affect modern magnet materials, unless sufficient tophysically damage the material.

Modern magnet materials do lose avery small fraction of their magnetism over time. For samarium cobaltmaterials, for example, this has been shown to be less that 1% over a period often years.

If a magnet is stored away from power lines, othermagnets, high temperatures, and other factors that adversely affect the magnet,it will retain its magnetism essentially forever.

Modern magnet materialsare made through casting, pressing and sintering, compression bonding,injection molding, extruding, or calendering processes.

Modern permanent magnetsare made of special alloys that have been found through research to createincreasingly better magnets. The most common families of magnet materials todayare ones made out of aluminum-nickel-cobalt (Alnico), strontium-iron (Ferrites,also known as Ferrites), neodymium-iron-boron (neo magnets, sometimes referredto as “supermagnets”), andsamarium-cobalt. (The samarium-cobalt an...

Magnets do the following things:Attract certain materials – such asiron, nickel, cobalt, certain steels and other alloys;Exert an attractive or repulsive force onother magnets (opposite poles attract, like poles repel);Have an effect on electrical conductorswhen the magnet and conductor are moving in relation to each other;Have an effect on the path taken byelectrically charged particles traveling...