Strong magnets are permanent magnets that are almost impossible to demagnetize. They came to a classification based on their composition. This is a neodymium iron boron, or NIB, samarium cobalt or SmCo, Alnico, and ceramics or ferrite.
Of the four magnets, neodymium iron boron and samarium cobalt are the strongest. two is also known as rare earth magnets because they are derived from compounds lanthanoid series are considered rare element in the periodic table. NIB and SmCo developed in the early 1970s.
Alnico magnet is a compound derived from the Aluminum, Nickel, and Cobalt. It was first introduced in the 1940s. As the alnico magnet is not as strong as the previous two so can be demagnetized. Alnico magnets are also the most affected by temperature. Therefore, a horseshoe and the magnet bar should be treated with care to prevent them from losing magnet.
The most popular today is a ceramic magnet or ferrite. First developed in the 1960s, ceramic magnets are strong enough, but their magnetic strength varies with the temperature difference.
As a powerful magnet classified as permanent, they can be made into different shapes including round bars, donuts, ring, rectangle, disk, and custom shapes. Just as the magnet shape is important, the same way a magnet magnetizing significant.
Depending on the application, the magnets can be configured in various ways. For example, a ring magnet can be magnetized in the N and S on the outside. Or it can be a magnet S on one side and N on the other side. Another configuration is magnetizing magnet N on the bottom or S above.