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this post was submitted on 29 May 2025
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Interesting. I had no idea that UV rays demagnetize magnets.
It's the heat, not the UV: https://en.wikipedia.org/wiki/Curie_temperature
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.
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?
Thank you for the explanation!
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/