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A Permanently Magnetic Liquid
- userbinator 7y ago"Before our study, people always assumed that permanent magnets could only be made from solids." If you finely divide a magnet into tiny magnets and suspend these particles in a liquid, is that really a liquid magnet, or just a bunch of solid magnets floating in a liquid?
- Iv 7y agoTechnically, it is called a colloid. Like milk or blood. https://en.wikipedia.org/wiki/Colloid https://en.wikipedia.org/wiki/Colloid
- jessriedel 7y agoThe physics-y way to answer this question is usually to define things in terms of the scales at which it's probed. If everything you can sense with macroscopic instruments is consistent with the liquid properties and the magnetic properties, it's a magnetic liquid. That it's "really" just solid magnets suspended in a liquid seems not much more relevant than the fact that solids are "really" fluids if you watch them on the astronomically long timescales on which they lose solid form due to tunneling. In this case, it's a liquid magnet down to roughly the scales of the nanoparticles, which is only a bit bigger than the atomic scale on which nothing is a normal liquid.
- foobar1962 7y agoThe tunneling sounds interesting. Can you post a reference?
- jessriedel 7y agoThe example is from a Freeman Dyson paper, but I wouldn't take it too seriously. https://physics.stackexchange.com/q/242654/7911 https://physics.stackexchange.com/q/242654/7911 There are better example from condensed matter physics.
- samplatt 7y agoAs I understand it (which, like most of the population of the planet, is not very much), solid magnets are also just a lot of smaller magnets floating in a macrostructure.
- jarfil 7y agoPermanent magnets are locked in place. If they're floating freely, the "tiny magnets" just snap together and cancel each other out. That's why heating (increasing particle mobility) a permanent magnet makes it lose its magnetization.
- NZGumboot 7y agoNot really floating, since that implies a certain freedom of movement that atoms in a solid don't have. But otherwise you are correct, since each electron is a tiny magnet (protons and neutrons are also magnets but their magnetic field strength is much smaller so they can safely be ignored). A macroscopic magnet is just a material where the electron magnetic fields add together to an macroscopically appreciable value, rather than cancelling each other out, i.e. the direction of the electron magnetic fields are largely aligned.
- liuhenry 7y agoYou've actually stumbled upon the central premise of this discovery. If you finely divide a magnet into tiny magnets and suspend the particles in a liquid, you get... a normal ferrofluid. It's magnetic in the presence of an external field, but will lose its magnetization once that field is removed. This is because permanent magnetism (i.e. ferromagnetism) is a bulk property. Every atom has a magnetic moment, but they are normally randomly aligned and thus the macroscopic field cancels out. It's only when these moments are aligned that a macroscopic magnetic field arises. Permanent magnets have the requisite crystalline structure for this to happen. As you chop it up, this macroscopic organization is destroyed. If you get into the details, what they've done is to use the surface tension of the oil-in-water to "jam" an outer layer of magnetic particles and prevent them from rotating, thus preserving their magnetic alignment. This, in turn, is apparently enough to keep the free-floating, unjammed particles inside the droplet aligned as well, thus turning the entire droplet into a magnet. Pretty interesting, because without the membrane, none of the ferrofluid is magnetic, but with the membrane, all of it is.
- yetihehe 7y agoSo essentially they made small jelly (not really fluid) magnets out of ferrofluid.
- stronglikedan 7y ago> small jelly More of a jam, since it contains solids. ;-)
- de_watcher 7y agoPSA: Don't eat magnets more than one at a time.
- Zanni 7y agoThis is a better explanation than the original article.
- 7y ago
- jarfil 7y agoIt's a magnet membrane surrounding a portion of liquid. On one side your right, this isn't really a "liquid magnet", but on the other, this behaves like a magnet while retaining many of the properties of a liquid.
- YayamiOmate 7y agoI think the question doesn't make sense, because if you take it further something interesting appears. If you do have tiny solid magnets in a liquid, why don't they rotate and cancel out? They clearly cannot do so because macro sample would lose its properties. It simply cannot be tiny magnets suspended in a liquid. You gotta provide finer definition of a liquid because it typically does not have a structure. In your example there are constraints to movement and position of tiny magnets.
- dhosek 7y agoGreat. Now we're one step closer to the T-1000.
- timemachine 7y agoCame to make the same comment.
- bryanrasmussen 7y agoI figure Skynet probably sent back an editorbot to flag your comment if you succeeded, but you tried your best to alter the future. John would be proud.
- daliusd 7y agoNice and appropriate username ;-) Unfortunately it is not reddit here.
- obiefernandez 7y agoAnd, even more curiously, the liquid can change shape - standing tall as a cylinder, flattening out like a pancake, round like a sphere, thinning out like a wire, or even more complex shapes, like… octopuses. Yep I thought the same thing.
- redis_mlc 7y agoThe T-1000 is one of the items on my "do not want" list. What's interesting is that Arnold at first was unsure of the Terminator script ... Arnold: "Ivan, this script ... is pretty weird ..." Director Ivan Reitman: "Yeah, perfect for you." After getting paid, Arnold bought an office building in LA. After a few more films and buildings, he was a billionaire, married into the Kennedy family, and became Governor of California, a stepping-stone to becoming President (had he been a born-American.) It all started with a weird film script. And back to the topic of materials, Arnold is literally a self-made man ... all of the Mr. Olympias trained themselves.
- lamchob 7y ago
- pontifier 7y agoThis may be useful in actually creating something I theorized about a few months ago. I call it a chemomagnet (as opposed to electromagnet). The basic premise is that individual magnetic domains are free to float and are unorganized until a chemical signal locks them into place in some sort of structure. The energy required to align and bind them would be chemical in nature, and once bound, another chemical signal could be sent to unbind them. The magnet would be controllable, like an electromagnet, but would not require any electricity at all to operate.
- kybernetikos 7y agoA bit like those heat packs where you click a metal disk inside them and they solidify, releasing heat? You could imagine doing the same but it 'turning on' a 'permanent' magnet.
- GistNoesis 7y agoIsn't a chemomagnet magnet just a scaled down version of a mechanical switchable magnet?
- yetihehe 7y agoYeah, but you could program it with any number and position of magnetic poles. Imagine a ring of this material as a stator in electric motor, you could reprogram it with 4 or 6 poles on the fly.
- dustfinger 7y agoliquid programable motors with possible temporal formation capabilities! Sounds one step closer to Skynet's liquid metal terminator :-) Fascinating!
- cr0sh 7y agoI wonder if your idea - or this "magnetic liquid" - could have application in "artificial muscles"? Fascinating to think about...
- exebook 7y agoIs it possible now to make a completely silent water/magnetic liquid cooler for a CPU by forcing this liquid to flow inside a heat pipe by a few electromagnets? Thus removing the noisy motor driven pump.