Why isn’t liquid iron still magnetic? Why can’t we have liquid magnets?
In: Physics
Ferromagnetism (the type of magnetism exhibited by iron) comes about because irons atoms, each of which is a tiny bar magnet for quantum mechanical reasons, line themselves up so their tiny magnets point in the same direction. These groups of atoms are called domains, and a piece of iron will be magnetic when all its domains line up too. That creates one macroscopic permanent magnetic field.
I say permanent because the magnetic field is not induced by an external source. That permanent field can be destroyed if the order of the magnetic domains is destroyed.
You may remember that when you heat up a substance you make its particles vibrate faster. Eventually they will vibrate fast enough to overcome the forces holding them together and change state (e.g. solid to liquid).
When you heat iron until it melts, you make its atoms vibrate so fast that their tiny little bar magnets no longer align, destroying the magnetic domains and hence the permanent field. You don’t even need to melt iron to do this. Heating a magnet to a sufficiently hot temperature will destroy the magnetic order.
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