Science Questions

Why are some magnets stronger than others?

Sun, 27th Jan 2008

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Luke asked:

I recently bought some tiny magnets from a hardware store to stick things up on my wall. I bought these magnets called rare earth magnets. They’re so strong that now I can’t unstick them from each other. It’s amazing, can you tell me how these tiny magnets that’re about 1.5cm in diameter, different from other magnets that don’t have the same kind of power?


On a fundamental minute scale iron, nickel and cobalt atoms have more electrons orbiting in one direction than the other.  This means they produce little, tiny currents like electromagnets.  With ferromagnetic things like iron, nickel and cobalt – these tend to like lining up into areas.  Normally if you just take these areas, the north poles of these little areas will attract south poles of other little areas.  They’ll all wind up going into circles and ovals in magnetism.  If you put them in a strong magnetic field they’ll all line up.  Normally with iron, if you take the magnetic field off, most of them will realign and then all the rest more randomly.

They get all jiggled up and end up pointing in random directions again. With very strong magnets, like rare earth magnets, the structure of the alloy tends to make it very hard to change the direction of the magnetic field.  This means that more of them stay lines up, and you get a stronger magnet.


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