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What is a permanent magnet?

A permanent magnet is one in which the magnetic property is inherent to the material itself, as opposed to being induced by some external action such as an electrical current.


Magnetism arises from a sub-atomic property called spin, which has no classical analogue, but can be thought of as being somewhat similar to rotation. The "direction" of the spin matters for a variety of atomic conditions, such as the Pauli Exclusion Principle, which states that the orbitals in an atom can only hold two electrons at a time, and those electrons must have opposite spins. Electrons in different orbitals are allowed to have the same spin. Spin is an electromagnetic property, and if two spins are in opposition to each other, their magnetic effect cancels out. If there are two or more unpaired electrons, however, they will produce a net magnetic effect.


Iron is the most common example of a magnetic material, but others such as liquid oxygen can also behave like permanent magnets due to these unpaired electrons. The real key is not just to have an atom with unpaired electrons, but also to get all those atoms to align their spins in the same direction, rather than randomly. When this happens, the magnetic effect will become apparent at the macroscopic level. 

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