is there an alloy that will be attracted to an electromagnetic but will not hold any residual magnetism?

[Wish i knew more]

I am designing an experiment in which I will need to suspend a small amount of an alloy between a series of electromagnets. Is there an alloy that I could use that will be able to be suspended between electromagnets without actually touching them and will not hold any residual magnetism or at the most hold magnetism for a very short period of time? To be honest I'm not even sure if an electromagnet will magnetise metal like other types of magnets will. Any and all input is greatly appreciated. Thanks for your time.

[Externet]

Not an alloy but pure iron will do it.

[Wish i knew more]

I don't know much about magnetism but I thought when exposed to a strong magnetic field for an extended period of time that pure iron would remain magnetised after the magnetic field was removed?If not that would be affordable and the perfect solution. I tried searching the internet but all I can seem to find is explanations on how magnetism works and nothing on the effects of magnetism on different metals.

[swansont]

Copper, aluminum or titanium are all nonmagnetic, so I expect alloys of these materials are candidates. Some kinds of brass are nonmagnetic, too.

[Moontanman]

I don't know much about magnetism but I thought when exposed to a strong magnetic field for an extended period of time that pure iron would remain magnetised after the magnetic field was removed?If not that would be affordable and the perfect solution. I tried searching the internet but all I can seem to find is explanations on how magnetism works and nothing on the effects of magnetism on different metals.

 

 

Just a common iron nail will work in that context, remove the current the magnetic field disappears...

[ewmon]

Not knowing any more than this, I know that the steels are iron alloys with various other elements and of various proportions, so there might be a steel that comes close to what you want.

 

A silly question, but have you gone here or here?

[swansont]

Not sure why iron has been suggested. I think iron fails the requirements of "suspended between electromagnets without actually touching them" and "will not hold any residual magnetism". I take the former to mean that it's not attracted, and iron will tend to develop residual magnetism.

[Wish i knew more]

That's what I thought. I'm not sure if there is even any type of metal or alloy that will be attracted to magnetism without developing residual magnetism. I was thinking that I might have to use an alloy that will be very lightly attracted to magnetism and increase the strength of the electromagnets. If I can reduce the time that it will be exposed to the electromagnets to a few seconds hopefully this will prevent the material from developing residual magnetism or at least make it dissipate quickly but this still leaves the question of what type to use unfortunately.

[swansont]

If you want something that won't develop residual magnetism, stay away from ferromagnetic materials. If you want attraction but only when the field is on, that's paramagnetism. (repulsion in the presence of a field is diamagnetism)

[Wish i knew more]

Good to know. Glad I joined this forum, I will have to look into paramagnetic materials

[Klaynos]

You could probably do it with either a paramagnetic material or diamagnetic material depending on the field set up.

 

(On a side not to the other posts IIRC steel has a lower residual magnetism than iron.)

[Wish i knew more]

I was able to find some info from everyone's help. Currently considering using tungsten as it is fairly easy to get and at a reasonable price. If I was understanding what I was reading than it seems to have stronger paramagnetic properties than most as well. Haven't looked into diamagnetic materials yet. I appreciate everyone's input, it has all definitely helped guide and speed up everything. Who's knows how long it would have been before I found out about diamagnetic and paramagnetic properties/materials.

[Wish i knew more]

I've been trying to figure out which rare earth elements have the strongest attractions to magnetism. Terbium sounded good until I found out the health risks and that it could catch on fire or explode if exposed to water... a bit to unsafe for me to use I think unless I can manage to set up a controlled environment and get a self contained respirator lol. Any ideas on what I could use that would have the strongest paramagnetic attractions but be relatively safe to use? I'm going to need to do a lot of studying before I can figure out all this on my own. I still plan on studying and learning as much as I can on magnetism as I go along but would prefer it not to slow things down. Also if there are any books that you know of that would be good for a beginner like myself that I could buy it would be a big help. I don't want to order one and have it be way over my head and not be able to understand it.

[Enthalpy]

Different points:

 

Ferromagnetic materials will feel a big force in a strong field like 1T, but you can reduce the field! So much easier.

Para and diamagnetic materials, as opposed, feel a very weak force, observable only if you hold them under a wire. And then you'd need a strong field, which is inherently dangerous.

 

Ferromagnetic materials can keep a very weak magnetization. Such materials are called "soft" ferromagnetic. Very common, because they were developed for transformers, electric machines, shielding, measurement instruments... Pure iron is one but has drawbacks; less pure iron with added silicon makes the common transformer laminations, cheap and easy to buy, hence I recommend it combined with a weak field; special alloys like Permalloy are extremely soft, characterized by the small coercive field in A/m.

 

You want as well your electromagnets to keep a very small magnetization! So they must be made of soft material as well. Or use coils without a nucleus, as the effect is already very clear.

 

Ferromagnetism is a molecular property, not an atomic one. Some stainless steels are non-magnetic, while Mn-Zn is a commonly used ferromagnetic material and CrO₂ a permanent magnet.

 

Forget about tungsten and terbium, that's the wrong direction. Anyway, rare earth are used in permanent magnets but are only one element of the molecule, like Nd-Fe-B or Sm-Co. The pure element won't give anything interesting.

 

Wikipedia has certainly good articles.

[John Cuthber]

Holding something suspended by an electromagnet without including a feedback system of some sort is, I think, a pipe-dream. (you might be able to do it with a rotating field, but it's still going to be horribly complicated.

However if you can turn the system upside down and hold the material up by eddy current repulsion from below then that makes things a lot easier.

[Enthalpy]

Oops, maybe I misunderstood the initial query of this discussion, indeed.

 

OP, could you give more details about "suspend between electromagnets without actually touching them"?

Do you mean: levitate? Or suspend them under a wire and observe the effect of the magnets?

[Externet]

There is a bunch of gadgets in the market that perform the levitation trick, as :

 

http://www.amazon.com/Fascinations-Levitron-Revolution-Platform-Technology/dp/B003BWSW0E/ref=sr_1_16?ie=UTF8&qid=1344615073&sr=8-16&keywords=magnet+globe

 

http://www.amazon.com/Anti-Gravity-Levitating-Globe-Realistic/dp/B004T4MIBM/ref=sr_1_12?ie=UTF8&qid=1344615073&sr=8-12&keywords=magnet+globe

 

http://www.amazon.com/Fascinations-LEVG33-Levitron-Globe-Ion/dp/B002R600BY/ref=sr_1_9?ie=UTF8&qid=1344615073&sr=8-9&keywords=magnet+globe

 

http://www.amazon.com/3-5-Floating-Globe-Magnetic-Levitating/dp/B0007KRXGM/ref=sr_1_3?ie=UTF8&qid=1344615073&sr=8-3&keywords=magnet+globe

 

http://www.amazon.com/Fascinations-Levitron-Globe-World-Stage/dp/B002W8IH4Y/ref=sr_1_2?ie=UTF8&qid=1344615073&sr=8-2&keywords=magnet+globe

 

http://www.amazon.com/Discovery-Channel-LEVG4-Floating-Desktop/dp/B000HZGM9G/ref=sr_1_1?ie=UTF8&qid=1344615073&sr=8-1&keywords=magnet+globe,

 

These use plain soft iron with the least possible amount of alloying carbon to keep magnetic remanence Br to a minimum.

[Wish i knew more]

By suspended I meant to be floating and not be influenced by any outside force other than magnetism. I was hoping to try and build 6 electromagnets and place them in a circle equally spaced so that they would equally attract the paramagnetic material in each direction causing it to float in the middle. I know it would be difficult in the sense that all 6 electromagnets would have to be the exact same strength otherwise it might draw the material to one magnet instead of staying in the middle. what is dangerous about using strong magnetic fields? Also I was wondering if the magnetic fields from the electromagnets would effect each other since I would need them to be close enough for all 6 to draw against the material... would I need to try and sheild the electromagnets from the ones next to it?

[John Cuthber]

It won't work

http://en.wikipedia.org/wiki/Earnshaw%27s_theorem

[chilled_fluorine]

I'm going to assume that superconductors are out of the question, right? If it doesn't need to be demagnetized immediately, you could just use iron, and heat it to its curie temperature afterwards. Try 300 C. I'm pretty sure it's less though.

[John Cuthber]

I'm going to assume that superconductors are out of the question, right? If it doesn't need to be demagnetized immediately, you could just use iron, and heat it to its curie temperature afterwards. Try 300 C. I'm pretty sure it's less though.

A few clicks of the mouse tells me that the Curie temp of iron is rather higher than that (770).

And it still won't work.

Earnshaw's theorem isn't just a suggestion: it's a mathematical proof.

 

You might be able to arrange for a lump of Gd in a strong temperature gradient to levitate in some sort of stable manner, but that requires an energy input and if you are going to do that it's probably easier to use a feedback system.

[Wish i knew more]

Thanks for the great reference. Slightly disappointing but motivating to to find another way. So if I understand it correctly I could use diamagnetic material being repulsed by multiple directions to create pseudo-levitation?

[swansont]

As the link states, Earnshaw's theorem doesn't hold for diamagnetic materials. That's the only way to do pure magnetic levitation. However, you can create pseudo-confinement with rotation or feedback. http://en.wikipedia.org/wiki/Magnetic_levitation

[John Cuthber]

Earnshaw's theorem doesn't rule out diamagnetic levitation

[Stevey McFly]

The quick research revealed that you would need to have either Fe, Ni, or Co in the mixture to get yourself a magnetic alloy. Otherwise, they will be not attracted by a magnet. Also, you can check for some information about alloys here

http://www.americanspecialmetals.com/hastelloyb-3.html

didn't have much time to browse through it and find what I needed, buy maybe you will have more luck.

 

Cheers!

Edited November 21, 2012 by Stevey McFly