Bismuth Crystals Hold Magnet Suspended for 100 Years

[NightHawkInLight] has been playing around with the diamagnetic properties of bismuth. Diamagnetic materials get a lot of attention due to their strange ability to produce the opposite of the magnetic field going through them. In simpler terms, metals like iron are attracted to magnets; metals like bismuth repel them.

[NightHawkInLight] built his own interpretation of a common lab example used to demonstrate this remarkable property, a levitator. A levitator is made by sandwiching a magnet between two plates of diamagnetic material. One of the plates is given a magnetic field opposite of the magnet underneath it by a stronger magnet placed some distance away. When this is done, the magnet in between wants to repel away from the plate above, only to find that as it gets closer to the plate below it is equally repelled, creating a stable system.

Eventually the magnet above will need realignment, but [NightHawkInLight] assures us this is only once every 100 years. Video after the break.

34 thoughts on “Bismuth Crystals Hold Magnet Suspended for 100 Years

    1. Yea, I agree, but it makes me wonder if you attached a disc to the magnet you could have a “perpetual motion” device on your desk, start the disk spinning and with only air resistance to slow it down it should spin on its own for hours, better than a Newton’s cradle.

    1. I have long wanted to acquire some bismuth to test it’s viability for constructing frictionless bearings. Also for growing pretty crystals, doing thermoelectric stuff, and experimental alloying. The price skyrocketed since 2005 , but it was finally back down to earth last time I checked. If only I could find a local supplier that wasn’t overcharging, or an economical shipping method from china..

  1. I was going to buy a few kilos of Bi from china, at spot price, but the shipping is ridiculous. Everything I wanted to order would fit in a padded flat rate envelope, for $5.70 but I guess those don’t work for international shipments. The markup in America is ridiculous, who knows how we can get a group buy on a bismuth-filled slow boat from china?

    1. maersk does air freight at reasonable prices, my primary concerns would be export/import restrictions, dunno if there are any but one is often surprised how many barriers there can be to international shipping, most of them from the businesses themselves, some employ regional pricing that makes region locked video seem innocent.

    1. It’s a guess. And a poor one at that. A research group I was part of did some tests using ultra high purity bismuth single crystals grown in an argon atmosphere, and we were seeing a “fall” rate of 100um per week. It is unlikely the poly-crystalline material being used would give more than 1 month of free float.

        1. The diamagnetic force of bismuth is weak. Not enough to keep the floating magnet afloat all by itself. So most of its weight is lifted by another magnet, which is carefully aligned so that the bismuth only needs to provide a very small corrective force to keep it in the middle of the gap.

          I’ve heard these magnets lose their power over the course of a few hundred years (or so I’ve heard). So a tiny, and otherwise unnoticeable reduction in the amount of lift, might not be something the bismuth can continue to provide a correction against if it’s very, very weak (low quality).

        2. It fell because we were not using a lifting magnet. We were using a thin slab of bismuth diced from a single crystal, and levitating it over a large neodymium magnet. We also experimented with carbon-graphite, and that worked well also. In the case of the setup shown in this article, the small magnet would most likely move up toward the large lifting magnet over time.

    1. Newton would have a smartass response to that question… mumble mumble something about laws of motion, conservation of momentum, impulses and such. Fortunately he’s not around. The magnet quickly pulled up a nail which hit another nail and caused it to fly away.

  2. As far as the diamagnetic force of bismuth is considered, it is not too strong, in fact not enough to keep the floating magnet afloat. Hence, the weight is lifted by another magnet. Being carefully aligned, the bismuth here only needs to provide a small corrective force, keeping it in the middle of the gap.

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