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What will happen to permanent magnet's magnetic field or magnetic ability if we keep same magnetic poles of two permanent magnet for long time?

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Will any magnetic loss happen over the long period of exposure or does the magnetic strength remain the same?

Sorry if my logic is wrong. Please explain this.

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  • $\begingroup$ I suspect that there will be a strong material dependence. I mean, we have soft iron, which basically cannot hold any magnetic field, and we have strong permanent magnets that do not need a field keeper to stay strong. I guess that every magnet material that we have has its own, distinctive external field strength at which it starts giving in to that external field. $\endgroup$
    – cmaster - reinstate monica
    Commented Jan 23, 2020 at 7:41

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If we keep two magnets with same poles together, then they'll become weaker overtime. I once deliberately did it to find out what would happen.

This could be explained with Magnetic Domain Theory. In magnets, the magnetic domains are aligned in the same direction, giving them a strong magnetic field. If two magnets are kept with like poles facing each other,

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... the effect will be similar to applying an external magnetic field to the magnet in direction opposite to the magnetic field of the magnet. This will result in the magnetic domains trying to align with the external magnetic field, and in this case, as the magnetic fields of both magnets are equal, some of the domains will disorient, thus weakening the magnetic field of each magnet,

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In my experience (with ferroxcube materials) nothing happens. In fact, to change the magnetic properties the magnetic domains inside must be reoriented. But the force excerted by the second magnet is not strong enough to do so. But one can magnetize a non-magnetic piece of iron (for instance the tip of a screwdriver) by moving it over a magnet.

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  • $\begingroup$ +1 If we force keep the magnet for long time will it loose magnetic strength ? $\endgroup$
    – Ganapathy C
    Commented Dec 11, 2014 at 11:33
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They will repel each other and slowly they will lose their magnetic property which is also called demagnetization

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I'm trying this now. I have 2 magnets (round with hole in middle). One is suspended on top of the other with a 1/2"plastic pipe.This site won't accept my pic as is. I believe energy is being used to keep the one magnete suspended. As a result, these magnets will lose their strength and eventually join together.

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  • $\begingroup$ Sorry, but that's not quite correct. Energy is used in the process of the 2 magnets demagnetizing each other, but no energy is used just by the magnetic repulsion. Similarly, if you put a brick on a table, no energy is consumed by the table supporting the brick against gravity. $\endgroup$
    – PM 2Ring
    Commented Jan 23, 2020 at 10:38
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By the way you describe it strong magnets will be produced. Powder from magnetic dipols is pressed together under the influence of a strong magnetic field. But in your case the addhesive forces during the time one press the two magnets together are not strong enouth to overlay the magnetic force. And the magnetic dipols in the two magnets don't get disorientated. So your magnets never will stick together.

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In this case if the 2 magnets are touching each other forcely with same pole then they will be act as a one another magnet whose 2 side are north and south but the touching point is mid point. But when they are not in touch they will repulse each other.

For this reason when we cut a magnet into 2 pieces then we get 2 new magnets.

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