Ferromagnetism (permanent magnetism in iron and iron alloys) happens when iron atoms (that are small magnets themselves) align to sum their magnetic fields and form a strong one we can experience in the macroscopic world.

When the magnet is heated, atoms are more energetic and more free to move around, they misalign because each atom is repelled by the others (equal poles repel each other, so when aligned they are in a constant state of repulsion, but if the material is cold they are "locked in") and the magnetic field disappears.

[–] threelonmusketeers@sh.itjust.works 1 points 2 days ago (1 children)

they misalign because each atom is repelled by the others (equal poles repel each other, so when aligned they are in a constant state of repulsion

I'm not sure this is true. When aligned, aren't all the domains lined up north to south, which would be a state of attraction?

[–] thepreciousboar@lemm.ee 1 points 23 hours ago

There's still atom-to-arom repulsion because of electron shells (that are negatovely charged) and attraction because of electron pairs forming a crystal bond, and other factors I don't know about.

My explaination is a gross oversimplification, and crystal chemistry is hard, but it should give a hint of what is going on.

[–] Drusas@fedia.io 1 points 5 days ago

Thank you for the explanation!

[–] zero_spelled_with_an_ecks@programming.dev 5 points 6 days ago

I think it's just the heat itself. Seems to be what a lot of magnet sites say like https://jdamagnet.com/demagnetization-of-permanent-magnet/