Electromagnetism Resource

Permanent magnets are capable of holding a permanent magnetic field. Many of these materials are ferromagnetic, in the sense that they use ferromagnetism to hold their magnetic field. Most common magnetic materials such as iron, nickel, cobalt and their alloys are ferromagnetic.

Permanent magnets are usually made of "hard" magnetic materials, in the sense that:

• hard magnetic materials retain their magnetic field after an external field is removed; and
• hard magnetic materials are difficult to magnetise and de-magnetise using an external magnetic field.

Hard magnetic materials are useful in:

• permanent magnets, such as in loudspeakers, fridge magnets, actuators, dc motors;
• information storage such as swipe cards and hard drives.