Different materials react very differently in the presence of a magnet. Metals such as iron, nickel and cobalt are strongly attracted to magnets and are known as ferromagnetic metals. Other materials may be weakly attracted, and there are even metals that are repelled by magnets. Ferrous metals are not only attracted to magnets but can be magnetized themselves by being exposed to magnets.
Ferromagnetic metals are strongly attracted to magnetic fields and are able to retain their magnetic properties after the magnet is removed. They are used to make permanent magnets. The main ferromagnetic metals are iron, nickel, cobalt, gadolinium and dysprosium. If you hold a piece of a ferromagnetic metal near a magnet, the attraction is strong enough to be felt.
Ferromagnetic alloys are alloys such as steel that contain ferromagnetic metals. Steel is a combination of iron and several other metals, and has a greater hardness than iron. Steel can retain its magnetism longer than iron because of this hardness. When heated to a high temperature, steel will lose its magnetic properties. This will also happen with ferromagnetic metals such as nickel.
Ferrimagnetic materials include ferrites, magnetite and lodestone. These all have iron oxides as their main component, as well as oxides of other metals. Human beings first discovered magnetism using lodestones. Lodestone is magnetite that is found naturally magnetized. Magnetite is attracted to magnetic fields but does not normally become magnetized itself. Ferrimagnetic materials are similar to ferromagnetics, but with a lower magnetic attraction.
Paramagnetic metals are weakly attracted to a magnet, and do not retain magnetic properties when the magnet is removed. They include copper, aluminum and platinum. The magnetic properties of paramagnetic metals are affected by temperature, and aluminum, uranium and platinum become more attracted to magnetic fields when they are very cold. Paramagnetic substances have much lower attractions to magnets than ferromagnetic materials, and sensitive instruments are needed to measure the magnetic attraction.
- Stockbyte/Stockbyte/Getty Images