Why are iron, cobalt, and nickel magnetic, but other metals are not?

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Why are iron, cobalt, and nickel magnetic, but other metals are not?

In: Physics

To Eli5, while this doesn’t cover all of it, metals form in crystalline structures, and there are a few different types. Some types arrange the electrons so that they are magnetic and others don’t (they are all magnetic, just to greatly different degrees). Also, most metals and metal alloys can be forced into different crystal structures by cooling slowly or rapidly.

Take steel for example. Based on its heating and cooling method, and its atomic mixture, it can form various crystal structures. This site has a good explanation and pictures. https://www.outokumpu.com/expertise/2020/the-stainless-steel-family#:~:text=All%20steels%20are%20an%20alloy%20of%20iron%20and,a%20gamma-iron%20face-centered-cubic%20%28fcc%29%20lattice%20–%20forming%20austenite.

This is a really complex topic, but to start, electrons act basically as tiny little magnets. They have a North Pole and a South Pole, and put out a tiny magnetic field.

In a lot of elements, electrons pair up, pointing in opposite directions, and mostly cancel out the magnetism, but some elements have unpaired electrons, which lets the magnetism add up, instead of cancelling.

Even this isn’t enough though. Some atoms like to line up facing opposite directions, cancelling the magnetism. Only certain elements like lining up all in the same direction, creating an even stronger magnetic field.

These atoms are called “ferromagnetic”, and that’s the type of magnetism you’re talking about. Because all their atoms like lining up in the same direction, and they have unpaired electrons, they can create a magnetic field, and respond strongly to outside magnetic fields.

As for why certain metals like lining up one way vs the other, that’s some quantum stuff that’s way outside the scope of an ELI5.

By the way, I skipped over a bunch, cause again, this is a really complex topic, but that should be enough to give you an idea.

The shape of the atom. They have a dangling electron which gives the thing polarity. If enough atoms are pointed the same way, the effects of those electrons sum up to macro-level effects like magnetism.

To add on to everyone saying the atoms are pointing in the same direction, they’re not really pointing, we just use arrows to indicate the direction of a magnetic field. In reality, magnetic fields are circular.

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It has to do with the crystalline structure of the thing thats magnetic. As some eluded to, individual atoms have electrons that orbit the nucleus in a certain direction or spin. If, when all joined together in their crystalline structure. The perimeter of the molecular configuration has all electrons traveling in the same direction, then the thing is magnetic. It just happens that it occurs in some alloys and metals but it can happen in other things too, specifically things that are doped to force magnetic configuration.

How has no one figured it anyway to magnetise aluminium ?

I just have to put a top level comment here to point out I hadn’t realised that cobalt and nickel are magnetic metals and want to thank the OP for pointing that out to me.

To have a magnetic you need a magnetic field, to have a magnetic field you need charges to be in motion and a force. You can either cause this by a current following into an element or alloy or the element itself would have it’s own particles in motion.

You see elements want to be in a stable state outside of chaos and to have that stable you need to have the same number of protons which are a positive particle and electrons that is a negative particle in which case the protons are centered inside the electrons and the electrons are around the protons in shells the first shell will have 2 electrons while the rest will have up to 8 and 8 electrons on the shell basically makes it very stable like having a highway with proper exists and traffic control but when the number isn’t 8 the electrons aren’t stable so they want more electrons to be stable.

The thing is iron, cobalt and nickel like other transition metals don’t have a number of protons to accommodate that number of electrons to become stable so how do these guys stabilize? Instead of only using their valence electrons they also use the shell below it when that happens you have the electrons travel in motion and they have a velocity and they cause a centripetal force and what happens is you get a magnetic field that is perpendicular to this force and electron motion basically [like this picture](https://www.pasco.com/products/guides/right-hand-rule).

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tl/dr: Those elements got an unstable outter shell which gets the bois from the lower shell to do their dirty work which pisses off the laws of nature but their screams go the wrong way. Kinda like outsourcing….

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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