HELP! Demagnetization 2

[lodestone]

My questions are similar to one in another thread. In my application, I'm using two rare-earth magnets inside a shaft, same poles touching to repel each other (thus moving a rod inside the shaft)and then bringing them together again (no impact), then repelling, over and over...

1)Should I expect the magnets to demagnetize or even one of them reverse poles over time?

2)If I find the rare-earth magnets to be too strong (too hard to bring together) for my application, could I use ceramic or ferrite magnets instead, or would these be even more subject to demagnetization or reversal?

Many thanks in advance.

 

[electricpete]

At room temperature, Neodimium type magnets are not likely to become demagnetized as a result of seeing a reverse field. Ferrite and AlNiCo are more likely to become demagnetized quickly in that situation.

Temperature is one variable to consider. Any permanent magnet becomes demagnetized quicker as you approach its Curie temperature.

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(2B)+(2B)' ?

 

[lodestone]

Thanks electricpete. This application would only be subject to ambient indoor temperatures, so 32 to 95 degrees fahrenheit (0 to 35 degrees celsius). What is the Curie temperature for Neodimium magnets anyways?

 

[electricpete]

The Curie temperature for Neodimium magnets is around 310C.

http://en.wikipedia.org/wiki/Neodymium_magnet

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(2B)+(2B)' ?

 

[lodestone]

Pete, in your first reply, did you say that the poles of (I'm assuming) one magnet could reverse? If so, could I end up with the two magnets suddenly being attracted to each other instead of repelled?

 

[RyreInc]

If demagnetization isn't an issue than neither is field reversal. Both are caused by a field opposing the magnet's; the field required for reversal being much greater than that for demagnetization.

 

[lodestone]

Thanks RyreInc.

 

[sreid]

Ceramic magnets will not demagnitize due to a reversed field. Ceramic 5 is a typical material these days.

 

[RyreInc]

sreid, That's a bold statement! Any magnet can be demagnetized, the field just needs to be strong enough.

 

[sreid]

Sorry, In the context of the OP [like poles forced together], ceramic magnets will not demagnetize.