Magnets

Magnets are materials that creates a magnetic field of their own. Extreme examples of magnets are "hard", or "permanent" magnets (like refrigerator magnets), which remember how they have been magnetized, and "soft", or "impermanent" magnets (like the material of the refrigerator door), which lose their memory of previous magnetizations. "Soft" magnets are often used in electromagnets to enhance (often by factors of hundreds or thousands) the magnetic field of a current-carrying wire that has been wrapped in the region of the magnet; when the current increases, so does the field of the "soft" magnet, which is much larger than the field due to the current. Permanent magnets occur naturally in some rocks, mainly lodestone, but they are now more commonly manufactured.
Materials without a permanent magnetic moment can, in the occurrence of magnetic fields, be attracted (paramagnetic), or repelled (diamagnetic). Liquid oxygen is paramagnetic; graphite is diamagnetic. "Soft" magnets, which are powerfully attracted to magnetic fields, can be thought of as strongly paramagnetic; superconductors, which are strongly repelled by magnetic fields, can be thought of as strongly diamagnetic.