Neodymium Magnet (demagnetising process)

[samelt]

Hi

 

Can you tell me if neodymium magnets (it measures only a few cm's) can be demagnetized with another magnet? and what the process is required to do it and how long it takes?

 

Thanks

[DrP]

I seem to remember that high temperature can kill a Neodymium magnet. I would assume that they can be demagnetise by another magnet but I would not how long it would take. Impact can demag a magnet too.... but the Nd ones are brittle so are more likely to break than demagnetise.

[Externet]

There was a Nd magnet for years holding a deflecting aluminium foil for stray ambers on my standalone fireplace wall.

 

It dropped as a dead fly a day the temperature was raised considerably. I cannot tell how many degrees, but that data has to be available on the net. So yes, that is one sure way to turn a magnet into a piece of metal.

[imatfaal]

There was a Nd magnet for years holding a deflecting aluminium foil for stray ambers on my standalone fireplace wall.

 

It dropped as a dead fly a day the temperature was raised considerably. I cannot tell how many degrees, but that data has to be available on the net. So yes, that is one sure way to turn a magnet into a piece of metal.

 

The Curie Point of a Neodymium Magnet is 320 C

[DrP]

I bought a 2.5 x 2.5 x 1 inch neodymium 52M block earlier in the year - it was a super fridge magnet for 6 months or so which had about 5 or 6 coins stuck end to end projecting out from the fridge on it in a perfectly horizontal line. I assume there are more sensible uses for such a thing, but hey - coin levitation was cool for a bit... visitors would comment on the power of my fridge magnet when they saw the coins tip to tip projecting out into the room.

 

It's in my car now - I can't tell you why it is in there because I undertook an illegal act with it - lol... just for fun and to see if it would work. It did!

 

I too am wondering if it as strong as when I first got it.

Edited August 9, 2016 by DrP

[Enthalpy]

Heat is a good solution.

 

An other permanent magnet wouldn't demagnetize a Nd magnet because it wouldn't be strong enough. Nd magnets keep their full magnetization even it assembled head-to-head so no flux passes through. It makes designs using them much easier than with older magnets like AlNiCo.

 

A strong alternating and damped magnetic field would demagnetize a Nd magnet. It needs like 3T hence can't use a permanent magnet nor a magnetic circuit. The spool that creates this induction consumes several MW which can be provided by the discharge of a really big capacitor, a fraction of m³; the oscillating current suggests a nonpolarized capacitor which is even bulkier.

 

I did nearly this to magnetize SmCo magnets. An oven is easier.

[samelt]

A strong alternating and damped magnetic field would demagnetize a Nd magnet. It needs like 3T hence can't use a permanent magnet nor a magnetic circuit. The spool that creates this induction consumes several MW which can be provided by the discharge of a really big capacitor, a fraction of m³; the oscillating current suggests a nonpolarized capacitor which is even bulkier.

 

Heat is a good solution.

 

An other permanent magnet wouldn't demagnetize a Nd magnet because it wouldn't be strong enough. Nd magnets keep their full magnetization even it assembled head-to-head so no flux passes through. It makes designs using them much easier than with older magnets like AlNiCo.

 

A strong alternating and damped magnetic field would demagnetize a Nd magnet. It needs like 3T hence can't use a permanent magnet nor a magnetic circuit. The spool that creates this induction consumes several MW which can be provided by the discharge of a really big capacitor, a fraction of m³; the oscillating current suggests a nonpolarized capacitor which is even bulkier.

 

I did nearly this to magnetize SmCo magnets. An oven is easier.

 

Thanks Enthalpy, being a complete beginner at this what is 3T? what type of capacitor would demagnatize the Nd magnets?

 

Thanks

[Enthalpy]

3 Tesla is a BIG induction. Even in a small volume, such an induction stores a big magnetic energy. The capacitor (bank) providing this energy plus the losses is bulky, like 0.2m³, and expensive. The coil and the circuit are difficult to design and build. So this isn't the good method. Heat your magnets instead.

[John Cuthber]

There seems to be a tacit assumption here that the OP wishes to demagnetize a magnet.

Perhaps he's just checking that his propose idea won't kill his magnet- or, at least, won't do it quickly.