Why are iron, cobalt, and nickel magnetic, but other metals are not?
In: Physics
Great question OP!
All materials fall into one of three catogories:
**Ferromagnetic:** In the presence of a magnet, becomes a magnet itself; very high attraction to a magnetic force.
***Eg: Iron, Nickel and Cobalt, Fe3O4 (Ferrite), NdFeB (“Neodymium” magnets), AlNiCo (Another common material used for magnets).***
**Paramagnetic:** Attracted to a magnet but does not become a magnet itself.
***Eg: Gadolinium, Tungsten, liquid oxygen.***
**Diamagnetic:** Compound is repelled by a magnetic field (Really incredible stuff!).
***Eg: Bismuth, Pyrolytic Graphite, Superconducting Materials.***
Whether a material can be magnetic at all depends on the amount of unpaired electrons in the atom. As atoms join together to form chemical structures, which electrons are paired and unpaired changes. If no atoms present in a material have any unpaired electrons, then the material won’t really respond to a magnet.
The majority of compounds that exist are either weakly paramagnetic or diamagnetic but to such an insignificant degree that we regard them as ‘non magnetic’.
Normally, a ferromagnetic material has to be magnetised first or it won’t be magnetic. By default, the unpaired electrons within each grain of the material are facing the same direction and acting as a magnet (AKA, a *domain*), but these grains (domains) are all randomly oriented within the material so the magnetic effect of all these domains cancels out.
When a magnet is brought close to a para/ferromagnetic material, the electron pairs allign in the direction of the magnetic field.
Now they would love to stay in their new arrangement, but a pesky little thing called heat keeps knocking them about the place and changing the orientation they are facing! Magnetic compounds have a very high resistance to this effect and so it takes a lot of heat energy to disrupt the orientation of the domains.
So **ferromagnetic materials** allign with a field and can stay that way once the magnet is gone, (up until the point where there is enough heat energy to knock them out of alignment, known as a materials *Curie Point/Temperature*).
**Paramagnetic materials** allign to a magnetic field while a magnet is present, but go back to being random once the magnet is taken away.
**Diamagnetic materials** allign opposite to/against the magnetic field, but return to normal once the magnet is removed.
It stands to reason that there should be a fourth category of materials that are ***‘Ferrodiamagnetic’*** which allign against a magnetic field and stay that way after the magnet has been taken away; alas to my knowledge, no such material has been found to exist.
I hope this answers some of your questions you have OP (and anybody else who has read this!)
^(Magnetism is a strange thing and even weirder to wrap your head around! I’m always looking for new ways of understanding magnetism so I’m interested in seeing what others have to say!)
**TLDR**; Wibbly Wobbly Sciency Wyiency magic.
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