5 ms·
What Materials Are Magnetic?
- FrankWilhoit 2y agoTheir example of nickel is a U. S. five-cent coin. Nickel is ferromagnetic, but the coin is 75% copper and a magnet will not pick it up.
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- barelyauser 2y agoBut they can be picked up with right kind of electromagnetic arrangement[0]. [0]. https://youtu.be/7ZeBWJLRXqM&t=1231 https://youtu.be/7ZeBWJLRXqM&t=1231
- m463 2y agoI have a shrunken nickel from these folks: https://www.capturedlightning.com/frames/interesting1.html https://www.capturedlightning.com/frames/interesting1.html Don't know if the copper figures into the shrinking...
- analog31 2y agoInterestingly, the Canadian coins are the same dimensions, but are magnetic. US vending machines used to have a magnet that would deflect Canadian coins into the coin return slot. When I was growing up near Detroit, merchants took US and Canadian coins interchangeably, and gave both back out as change. But the Post Office was strict about it. I managed to collect a set of King George coins -- at least the smaller ones.
- eth0up 2y agoAnd some Canadian coins used be actual sterling, until they went to 80%ag. I think US coins were always 90. A few nickels from the early 1940s were, I think, 43% Ag, due to wartime metal shortages. But man, if you ever find a 1943 copper wheat penny in good to fair condition, you can think about retiring. The 1943 steel penny goes for about < $2.00 on average.
- bediger4000 2y agoTungsten carbide is magnetic. I bought a "tungsten" cube from some shoddy Amazon vendor. It's a lot denser than steel, but not as dense as pure tungsten. It is magnetic. The density of the cube is in the range of tungsten carbide.
- foobarian 2y agoI got one of those too, and it came with a manifest showing that there is about 5% of nickel in the composition so not too surprising. I would certainly be surprised if they could manufacture a pure cube (> 99.9%) for the price they sell it at :-)
- matsemann 2y agoWhat are you using the cubes for?
- extraduder_ire 2y agoThe most common use for tungsten cubes is as a kind of spooky ornament. Encountering a 4 inch cube that weighs over forty pounds is pretty weird.
- cyberax 2y ago> Tungsten carbide is magnetic Pure tungsten carbide is not. You just got some magnetic contaminants in it. This has is a good test for fake "gold" that can consist of tungsten core with a thin film of gold on top. It's pretty much impossible to get pure tungsten, so such "gold" ends up being magnetic.
- mianos 2y agoThe glue to hold the sintered carbide powder is cobalt or iron or whatever pot-metal crap they have on hand for cheap blocks. That would be where the magnetism is coming from. If it's highly magnetic you probably have little tungsten and a lot of binder.
- rowanG077 2y ago
- dvh 2y agoLiquid oxygen is magnetic too (I think para in this case)
- mankyd 2y agoThat's mentioned at the bottom: "However, liquid oxygen and boron fullerenes (B80) are paramagnetic."
- m463 2y agoWonder if you could use that to separate gasses. I also wonder about "sorting" atoms/molecules like Maxwell's demon: https://en.wikipedia.org/wiki/Maxwell%27s_demon https://en.wikipedia.org/wiki/Maxwell%27s_demon
- thayne 2y agoIt's probably possible, but probably is less practical than other methods.
- mianos 2y agoThere are very specific about including 'metals' in every statement. Yep, paramagnetic non metals are: Oxygen (commonly shown on youtube), Nitric Oxide, Boron, Sulfur and some graphites (very slight) due to delocalised electrons.
- RavingGoat 2y agoMy smile of course :)
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- bsmith89 2y agoMost interesting sentence: > 304 stainless steel isn’t normally magnetic, but it becomes partially ferromagnetic if it’s bent at room temperature. Anyone have a lay-person explanation for this?
- koolba 2y agoNot a physicist, but I’d guess that bending the metal causes it to heat up, which in turn could make it easier for electrons to align and respond to magnetic waves.
- Tuna-Fish 2y agoIron exists in many different crystal structures in different kinds of steels. Some of these forms are magnetic, others are not. When you work the metal, such as by bending it, you can cause it to change from one structure to another. 304 is an austenitic stainless steel, and austenite is non-magnetic. But when it's cold worked, it turns into martensite, which is harder and magnetic. If you anneal it by heating it and letting it cool, it turns back into austenite.
- DoingIsLearning 2y agoVery cool, the site's entire 'materials' archives is really interesting as a layman in Materials Science. [0] This kind of reminded of the sense of wonder of reading through Encarta entries in the late 90's and how I assumed the internet would look like in the future. [0] https://sciencenotes.org/category/chemistry/materials/ https://sciencenotes.org/category/chemistry/materials/
- rkagerer 2y agoThat link lists the Piezoelectric Effect near the top. I wondered if there's a corollary for magnetism. I googled the word Piezomagnetic on a whim and was satisfied to find this: https://en.wikipedia.org/wiki/Piezomagnetism https://en.wikipedia.org/wiki/Piezomagnetism
- kergonath 2y agoIt is quite good. They touch on complex topics but remain understandable and provide sources for further reading. I did not see anything obviously suspect, which is rare in vulgarisation.
- SigmundA 2y agoSo aluminum and copper are listed as not magnetic yet powerful magnets are used to separate them from non metallic materials in recycling? Seems like a semantic argument. https://en.wikipedia.org/wiki/Eddy_current_separator https://en.wikipedia.org/wiki/Eddy_current_separator
- wtallis 2y ago> Seems like a semantic argument. That kind of phrasing usually indicates someone doesn't understand or is rejecting a meaningful and useful distinction. Is that what you intended to do here? The article seems to be pretty clear about how there are several different types of magnetism that can be exhibited by materials, and appropriately classifies various materials. Nothing about the existence or mechanism of eddy current separators is a counterexample to anything in the article.
- SigmundA 2y ago"Magnetism is the class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other." Aluminum is repelled by a strong magnetic field, hence the use of ECS, plastic is not. Aluminum is not Ferro-magentic it does however seem to be magnetic depending on the definition. https://en.wikipedia.org/wiki/Magnetism https://en.wikipedia.org/wiki/Magnetism The article itself on contradictory showing aluminium as nonmagnetic then classifying as paramagnetic, which is a type of magentisim, which is it?
- eth0up 2y agoI'm not a kid, but resemble one when I get a hold of a copper tube and strong neodymium magnet. Probably my favorite toy. I'm kind of glad I have only a kid's understanding of it.
- ianburrell 2y agoFrom the article: "Usually, when people talk about “magnetic metals,” they’re talking about ferromagnetic and ferrimagnetic metals." Ferromagnetic and paramagnetic materials behave differently. One sticks to a magnet, the other is slowed by a magnet.
- csours 2y agohttps://hackaday.com/2022/09/01/iron-nitrides-powerful-magnets-without-the-rare-earth-elements/ https://hackaday.com/2022/09/01/iron-nitrides-powerful-magne... Iron Nitrides
- mjfl 2y agoAt the microscopic level, what determines whether a given set of valence elections has an excess spin, and thus an excess magnetic moment, is still determined by an empirical set of rules, called Hund's rules, instead of from first principles, iirc: https://en.wikipedia.org/wiki/Hund%27s_rules https://en.wikipedia.org/wiki/Hund%27s_rules
- ChrisMarshallNY 2y agoI think I remember reading, somewhere, that liquid hydrogen is magnetic.
- ChrisMarshallNY 2y agoNah. Hydrogen under enough pressure, becomes metallic. I don’t think it’s magnetic, though.
- kergonath 2y agoGood question. The hydrogen atom does have unpaired electrons, but the H2 molecule does not and is diamagnetic. “Standard” solid hydrogen is a molecular solid so it is diamagnetic as well. Liquid H2 is also molecular and should be diamagnetic as well. I am not really familiar with metallic hydrogen but it would have metallic bonds and delocalised electrons, which can only be the 1s electrons. So the hydrogen atoms would not have any localised electron left, so no (orbital) magnetic moment. So yeah, I don’t think hydrogen is magnetic in any of its pure forms.
- fuzzfactor 2y agoIt's the oxygen when in liquid form.
- hilbert42 2y agoI reckon holmium deserved a mention, why is it missing? To quote Wiki: "Holmium, like all of the lanthanides, is paramagnetic at standard temperature and pressure. However, holmium is ferromagnetic at temperatures below 19 K (−254.2 °C; −425.5 °F). It has the highest magnetic moment (10.6 μB) of any naturally occurring element and possesses other unusual magnetic properties. When combined with yttrium, it forms highly magnetic compounds."