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Asked by JJD to Elizabeth, James, Martin, Martin, Rob on 16 Mar 2015.
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James Coombs OBrien answered on 16 Mar 2015:
Materials are magnetic because the atoms that make up the material get in line with a magnetic field. Form them to line up like this the have to be able to move. If they can’t move, they aren’t magnetic!
Thanks for your question!
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Robert Woolfson answered on 16 Mar 2015:
James is right, but it’s actually a little more complex than that. (I work in a lab that builds molecular magnets so this is sort of my area).
Materials are magnetic when they have electrons that are free to do things when they find themselves in a magnetic field. There are actually several types of magnetism. Most of the magnets we use, like fridge magnets, are permanently magnetic and so once we make them magnetic the electrons keep behaving as a magnet. This is called ferromagnetism.
Magnesium is very different, it’s a type of magnet called paramagnetic. This is much less usual, but more interesting because magnesium is only magnetic when you place it next to a magnet. If you take magnesium away from a magnetic field, it stops being a magnet. This happens because the electrons go back to an arrangement that’s not magnetic. But the next time the magnesium goes near a magnetic field it becomes magnetic again.
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Elizabeth Cooper answered on 17 Mar 2015:
Magnesium is paramagnetic. Paramagnetic means that if magnesium is placed near a magnetic field the electrons line up and magnesium becomes attracted to metal. If the magnetic field is removed the electrons go back to not be aligned and magnesium becomes not magnetic.
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