Rare Earth Magnet Degradation


by MassInertia
Tags: degradation, earth, magnet, rare
MassInertia
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#1
May21-11, 12:36 PM
P: 15
I have a bunch of rare earth magnets that I bought a few years ago. For the most part, they've been rather haphazardly stored in a jumbled mess, with a few others stuck on the refrigerator. Today I noticed that at least some of them are noticeably weaker (particularly noticeable with the strongest ones, as one would expect, I suppose). A quick Google search tells me that storing magnets near other magnets can weaken them, but I'm having difficulty finding more detailed information.

I'm wondering if anybody can give me some suggestions for long term storage. I have far too many (hundreds) to store them individually, except perhaps for the larger ones. I've put like with like in long chains and stuck them on the refrigerator (rather than just a jumbled mess), but I don't know if this is accomplishing anything useful. How much of a difference does storing them on a ferrous surface (like a refrigerator) make as opposed to storing them in isolation or attached to one another?

Also, there must be some nice equations or something out there that describe this degradation. Can anyone enlighten me?

Thanks.
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MassInertia
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#2
May24-11, 02:15 PM
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Bumpen
tiny-tim
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#3
May29-11, 03:56 PM
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Come on guys
someone must know the answer to this!

RedX
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#4
May29-11, 06:22 PM
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Rare Earth Magnet Degradation


I don't know much about magnets, but I'll give it a shot.

If the magnets are randomly placed next to each other, then I think it's the same as storing each independently, since on average, the magnetic field experienced by any one magnet from all the others would be zero.

But if you chain them, with North of one magnet connected to South of another, that's probably best (assuming you can pull them apart when needed), since if one magnet gets demagnetized it'll be re-magnetized by the other magnets.

I think the only thing you can really do wrong is to put North's next to North's and South's next to South's - but that's really hard to do since they repel when it's like this.

Storing them on a ferrous surface also ought to be good, since you'll magnetize the surface in such a way that they'll reinforce the fields of the magnets.
MassInertia
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#5
Jun2-11, 06:11 AM
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I'm really not interested in guesses. I have plenty of those myself.

I'm thinking I should ask this on an engineering forum rather than here.
RedX
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#6
Jun2-11, 12:06 PM
P: 969
Quote Quote by MassInertia View Post
I'm really not interested in guesses. I have plenty of those myself.

I'm thinking I should ask this on an engineering forum rather than here.
Here's a website:

http://www.coolmagnetman.com/magcare.htm

The last two are rare-earth magnets. Unfortunately, they say that it's almost impossible to demagnetize them, so you're doing something horribly wrong (if they're right). Basically if you just separate Neodymium-Iron-Boron magnets from your other magnets, you'll be fine, since they're so powerful. Also at the bottom of the page they give you practical ideas on how to channel the field by sticking ferrous surfaces to the magnets.
mikediezel
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#7
Dec9-12, 03:24 PM
P: 2
Ok, the answer is simple. When magnets come in close proximity of each other, they move the magnetic properties of the other, creating a magnetic flux. As this flux occurs over time, the magnetic properties weaken. It doesn't matter if it's an NeFeBr magnet or a regular ferrite magnet, it will lose it's properties just like a laptop battery loses its ability to charge and recharge over time. The Law of Conservation of Energy tells us that a magnet can retain its properties as long as it's not disturbed by other magnets, but the second it comes into contact that makes it react, degradation begins.
phinds
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#8
Dec9-12, 03:37 PM
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Quote Quote by mikediezel View Post
Ok, the answer is simple. When magnets come in close proximity of each other, they move the magnetic properties of the other, creating a magnetic flux. As this flux occurs over time, the magnetic properties weaken. It doesn't matter if it's an NeFeBr magnet or a regular ferrite magnet, it will lose it's properties just like a laptop battery loses its ability to charge and recharge over time. The Law of Conservation of Energy tells us that a magnet can retain its properties as long as it's not disturbed by other magnets, but the second it comes into contact that makes it react, degradation begins.
I don't understand how that can occur if you chain them. I've had a small set of rare earth magnets chained for a couple of years and I see zero degradation. Now that's not a quantified observation but I'm confident that if they have lost any of their power, it is VERY little. How does chaining them "disturb" them? Seems to me it would HELP, not hinder their ability to retain their strength.

The same is true of a pair that I have stuck on a filing cabinet. I can't feel any difference in the effort needed (quite a bit) to get them off the cabinet.
mikediezel
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#9
Dec9-12, 05:09 PM
P: 2
Very true about the combination of multiple magnets. Over the short-term, it does help to increase strength. However, when they remain bonded and are moved or excited, perhaps there is a metal object around them in storage that would aid in the movement of the particles. It could be wiring in the walls near the box they've been in or electrical movement in the fridge that would excite the particles. Earth movement, though it may seem minute, does have a large impact on the success of magnets.


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