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Author: Subject: Neodymium (NdFeB) magnets question
math
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shocked.gif posted on 19-11-2008 at 06:52
Neodymium (NdFeB) magnets question


hello,

I was wondering, as NdFeB magnets can de-magnetize almost all magnets of inferior class (ceramic, alfeco and samarium-fe), will this happen if I leave some NdFeB magnets of different sizes (mass, and also magnetic field power) stick together for a long time? :o



thank you


[Edited on 19-11-2008 by math]
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chief
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[*] posted on 19-11-2008 at 07:42


The good ones will not demagnetize; but heating them may destroy the magnetismus: Some don't make it beyound 110 Celsius, others last up to 350 .
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JustMe
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[*] posted on 19-11-2008 at 10:04


Interesting question. Dunno the answer, but I feel compelled to warn you that although small ones are easy to handle, if you get larger ones you really have to think ahead of what you are going to do while moving it.

Seriously, it can easly wipe a computer disk from distance, mess up CRT monitors permanently, and, if large and powerful enough, cause magnetically prone objects to come flying at you like in the cartoons (knives would be nasty). You can also break a bone if you place yourself between two large ones.

Other than that, have fun! I'd love to play with them but I have too much "dangerous" stuff (like that above) to consider it, LOL.
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[*] posted on 19-11-2008 at 11:55


I was aware that some strong NdFeB magnets lose magnetism at 80°C

Thank you for your hint, I'll await an answer to my question before getting stronger ones
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[*] posted on 19-11-2008 at 12:23


Unfortunately, the most strongly ferromagnetic materials have very low Curie points - the temperature at which loss of ferromagnetism occurs due to the magnitude of the thermal lattice vibrations making impossible the fixed spin-alignment of the unpaired d and f electrons that result in ferromagnetism. Apparently, unpaired electrons in 4f orbitals (lanthanides, which can have up to 7 unpaired f electrons in the middle of the series) and 5f (actinides, ditto) orbitals are more affected by thermal vibrations than d electrons.
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[*] posted on 19-11-2008 at 13:43


Thank you again, however my question was a lot less detailed and scientific, it just concerned the danger of de-magnetizing NdFeB magnets by keeping them stacked with larger (and stronger) ones of the same type.
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[*] posted on 19-11-2008 at 15:05


Quote:
Originally posted by math
Thank you again, however my question was a lot less detailed and scientific,
it just concerned the danger of de-magnetizing NdFeB magnets by keeping them
stacked with larger (and stronger) ones of the same type.


That can't happen the field strength required to permanently
reverse the residual induction exceeds the intrinsic coercivity
by 3 times. NdFeB is valued precisely because it withstands
opposing fields without degradation. Ordinary cermat behaves
as well.

.
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[*] posted on 19-11-2008 at 16:21


I meant to stack magnets together, not opposing their poles however your explanation covered that too I guess

I see...so they are more withstanding than regular ceramic magnets (which can be demagnetized by larger or forcing opposite poles together, AFAIK),
and being NdFeB the strongest class, they'd need a superior class in order to demagnetize them, not just a larger NdFeB magnet right?

Thank you very much, I'll look for a cheap supplier

[Edited on 20-11-2008 by math]
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