Magnetism is a phenomenon in which one material exerts forces of attraction on other materials.
There are a number of well-known materials that have demonstrable magnetic properties, including Nickel (Ni), Cobalt (Co), Neodymium (Nd), Samarium (Sm) and Iron (Fe), which are all ferromagnetic.
A common feature of ferromagnetic materials is that they comprise a very large number of small elementary magnets or magnetic domains.
External magnetic fields can move domain boundaries and turn entire domains, causing them to align and produce significant magnetic polarisation, with the result that the entire object acts as a magnet with a north and a south pole. A magnetised piece of one of these materials produces an external magnetic field after magnetisation and is called a permanent magnet.
We differentiate between permanent magnets, which produce a constant magnetic field, and electromagnets, which only produce a field when they are exposed to an electric current. An electropermanent magnet combines both these properties.
CHARGED WITH MAGNETISM
The most common method of magnetising a magnet involves placing it inside a coil and using a capacitor discharge to create a powerful magnetic field that the magnet then retains. The resulting magnetism depends on, among other factors, shape, quality and type of magnetisation. North at one end (pole) and South at the other is the most common type of magnetisation. There are a number of different types of magnetisation, e.g. bipolar, diametrical, radial and multipolar.
Neodymium magnets retain their enormous force without notable weakening. This is irrespective of whether the magnet is being used to lift something for years at a time or not used at all. Generally, the force weakens at a rate of approx. 10% every 100 years.
THE SAME MAGNET BUT MUCH STRONGER
Using iron/steel in combination with a magnet can enhance the magnetic force.
This creates what is known as a magnetic system.
Please note that magnetic systems are very sensitive to air gaps!