First-ever ferromagnetic liquid surprises researchers

Happy Saturday, friends Worldwide from Dr. TJ Gunn in Houston Texas USA

20 Jul 2019 / Physics World – magnetism and spin research update

Magnetic liquid
Spinning around: these three ferromagnetic liquid droplets are each about 2 mm long and are being spun on a magnetic stirring plate. The orange dye reveals their rotational motions. (Courtesy: Xubo Liu)

Permanent magnets made of small droplets of liquid have been created and studied by scientists in the US and China. The researchers believe that these are the first-ever liquid permanent magnets to be made. The shapes of the magnetized droplets can be changed, and this could lead to practical applications such as actuators for tiny soft robots.

www.madcitylabs.com
Advertisement

Many materials have magnetic moments that line up when exposed to an external magnetic field. In a ferromagnetic material (a permanent magnet), coupling between moments ensures that the material remains magnetic after the field has been removed. In other materials called paramagnets, thermal fluctuations quickly overcome the coupling once the external field has been removed and the material ceases to be magnetic.

Ferrofluids are paramagnets that consist of magnetic nanoparticles dispersed in a liquid. When exposed to a magnetic field, the combined effects of gravity, surface tension and the magnetic attraction between nanoparticles can create unusual spiky structures on the surfaces of ferrofluids. However, when the magnetic field is removed, ferrofluids return to a normal liquid state.

Rocket fuel

The first ferrofluids were created in the 1960s by a NASA scientist so that a magnetic field could be used transfer liquid fuel in low-gravity environments. While this use never came to fruition, ferrofluids have found several niche applications in more recent years – such as vacuum seals and dampers for loudspeakers. But the latest research could potentially give the materials a much wider range of uses.

Thomas Russell of the University of Massachusetts Amherst and Xubo Liu of the Beijing University of Chemical Technology made their discovery while working with scientists at the Lawrence Berkeley National Laboratory in California. The researchers were developing ways to create durable structures of one liquid within another by using a surfactant to create a layer of particles to surround the interior structure and prevent it from breaking up. This has allowed the researchers, for example, to create tubes of water within silicone oil.

Liu decided to try this with ferrofluids so that the structures could be manipulated magnetically. Using a 3D printer with an adapted nozzle, Liu injected millimeter-sized water droplets containing billions of iron oxide nanoparticles into toluene oil mixed with a surfactant. Normally the nanoparticles would simply diffuse within the droplets, but the surfactant pinned some of the nanoparticles to the inside of the droplets’ surface. As the nanoparticles built up, they jammed together and stopped moving, creating a kind of solid crust around the edge of the droplets.

Big surprise

Liu applied a magnetic field and found, as expected, that the droplets became magnetized. But the big surprise came when the field was switched off. Making measurements with a magnetometer, Liu discovered that droplets retained some amount of magnetization in the absence of an applied field.

Russell points out that the moments of the nanoparticles within the crust might be expected to retain a slight coupling once the field is removed, given how closely packed they are. But when carrying out the same experiment using progressively larger droplets, he and Liu observed that the remnant magnetization increased roughly in line with the droplets’ volume. This, he argues, implies that even the nanoparticles diffusing within the bulk of the liquid contribute to the droplets’ magnetization – and that as such the remnant magnetization is far larger than it would otherwise be.

Russell says that this is the first time anyone has observed ferromagnetism in a liquid rather than a solid. He admits that he cannot explain how the magnetism persists, given that the distance between nanoparticles within the bulk of the droplets is far larger than the typical separation of coupled moments within a solid. But he says he has no doubt that the liquid ferromagnetism is real. “There is a lot of talk about high-temperature superconductivity, but people don’t understand that either,” he adds.

Shape shifting

What is more, the shape and magnetic state of the droplets can be altered. The team transformed a ferromagnetic droplet into a cylinder by drawing it into to a narrow capillary tube, and showed the droplet remained magnetic by exposing it to a rotating magnetic field. They then turned the droplet back into a sphere by increasing the pH of the oil mixture to unstick the surfactants and nanoparticles. This also demagnetized the droplet, but they were able to remagnetize it with a simple bar magnet.READ MOREFerrofluid pump has no moving parts

The team describes the research in Science and writing in an accompanying commentary articleRémi Dreyfus of the CNRS in France and University of Pennsylvania says that the new research “challenges the established physics that ferromagnetic magnets can only be made of hard materials”. He also says that the work could have several applications, such as in the growing field of soft robotics – potentially allowing bulky pneumatic equipment to be replaced by smaller magnetically-operated actuators.

Dreyfus tells Physics World that the observed remnant magnetization is “puzzling” but says the lack of a clear explanation does not undermine the results. “The published data provided by the authors seem convincing to me,” he says.

Nevertheless, Russell says that he plans on getting to the bottom of the mystery. There are several tools that could be used to study the magnetic behavior inside the droplets, he says, including neutron scattering and electron microscopy. “There is quite strong interest in these materials,” he adds, “so I’m fairly confident we can get to the underpinning of this entire process”.

Edwin Cartlidge is a science writer based in Rome

25 Comments on First-ever ferromagnetic liquid surprises researchers

  1. Like!! I blog quite often and I genuinely thank you for your information. The article has truly peaked my interest.

  2. Having read this I believed it was extremely enlightening.

    I appreciate you spending some time and energy to put this information together.
    I once again find myself personally spending a lot of time both reading and leaving comments.

    But so what, it was still worthwhile!

  3. You can certainly see your skills in the article you write.

    The sector hopes for even more passionate writers
    such as you who are not afraid to say how they believe.
    All the time go after your heart.

  4. This is very interesting, You are a very skilled blogger.
    I have joined your rss feed and look forward to seeking more of your great post.
    Also, I’ve shared your site in my social networks!

  5. Right here is the perfect webpage for anyone who really wants to understand this topic.
    You realize a whole lot its almost hard to argue with you (not that I really would want to…HaHa).
    You definitely put a new spin on a subject that’s been discussed for many years.
    Wonderful stuff, just great!

  6. Hello, every time i used to check webpage posts here in the early hours in the dawn, since i like to gain knowledge
    of more and more.

  7. Its such as you learn my thoughts! You appear to understand so much about this, such as you wrote the guide in it or something.
    I think that you simply could do with a few percent to drive
    the message house a bit, but other than that, this is great blog.
    An excellent read. I’ll certainly be back.

  8. Hello, i think that i saw you visited my blog thus i came
    to “return the favor”.I’m attempting to find things to
    improve my web site!I suppose its ok to use a few of your ideas!!

  9. After checking out a handful of the blog articles on your
    web page, I seriously appreciate your way of blogging. I
    bookmarked it to my bookmark site list and will be checking back soon. Please visit my website too and tell me your opinion.

  10. Hi i am kavin, its my first time to commenting anywhere, when i read this article i thought i could also make comment due to
    this brilliant paragraph.

  11. We’re a bunch of volunteers and opening a new scheme in our
    community. Your website provided us with helpful information to work on. You’ve done a formidable process and our entire group will be thankful to you.

  12. This design is spectacular! You certainly know how to keep a reader entertained.

    Between your wit and your videos, I was
    almost moved to start my own blog (well, almost…HaHa!) Wonderful job.
    I really enjoyed what you had to say, and more than that, how you
    presented it. Too cool!

  13. Wonderful article! We will be linking to this great post on our website.
    Keep up the good writing.

  14. Hello! Do you know if they make any plugins to safeguard against hackers?
    I’m kinda paranoid about losing everything I’ve worked hard on. Any
    suggestions?

  15. I do believe all of the ideas you’ve presented on your
    post. They are very convincing and will certainly work.
    Nonetheless, the posts are too quick for beginners.
    Could you please extend them a little from
    subsequent time? Thanks for the post.

  16. My family every time say that I am wasting my time here at web, except I know
    I am getting know-how daily by reading thes pleasant content.

  17. I think this is one of the most important info for me. And i am glad reading your article.

    But wanna remark on few general things,
    The site style is ideal, the articles is really nice
    : D. Good job, cheers

  18. Hi, Neat post. There’s an issue along with your site in web explorer, may
    check this? IE still is the marketplace chief and a big component to people will pass over your magnificent
    writing due to this problem.

  19. Unquestionably believe that which you stated. Your favorite justification seemed to be on the web the easiest thing to be aware of.
    I say to you, I definitely get irked while people think about worries that they plainly
    don’t know about. You managed to hit the nail upon the top and also defined out the whole thing without having
    side-effects , people could take a signal.
    Will likely be back to get more. Thanks

  20. Hi to every one, it’s really a fastidious for me to
    pay a visit this site, it contains precious Information.

  21. Just desire to say your article is as surprising. The clearness on your put up
    is just cool and i can think you are an expert on this subject.

    Well along with your permission let me to seize your feed to stay
    up to date with forthcoming post. Thank you one million and please keep up the
    rewarding work.

  22. I have to thank you for the efforts you’ve put in writing this blog.

    I’m hoping to see the same high-grade blog posts from you later on as well.
    In truth, your creative writing abilities has encouraged me to get my own website now
    😉

  23. Haw has another prediction for that Bank continuing to move forward —
    fewer outright financial gifts and much more guarantors and cosigners.
    mortgage broker vancouver Rob: I mean, a guy along with your skills could go plenty of places to make easier money, right.v

  24. For more information, please contact the editor or publisher, or see our Terms and Conditions.

    mortgage broker Fill your complaint form on the NBC 5 Responds
    page or call 844-5RESPND , (844) 573-7763.v

  25. The measures, known as B-20 guidelines, require lenders to test a borrower’s power to
    pay at the greater with the Bank of Canada’s five-year benchmark rate or 2 percentage points higher compared to offered type of mortgage starting in January.
    mortgage calculator Upgrade your memory with a surgically implanted chip.v

Leave a comment

Your email address will not be published.