Why isn’t liquid iron still magnetic? Why can’t we have liquid magnets?
In: Physics
The high temperature prevents it from being magnetic. It loses its magnetism before it becomes liquid. Basically the heat is making the atoms move so fast they can’t properly line up to produce a magnetic field.
Ferromagnetism (the type of magnetism exhibited by iron) comes about because irons atoms, each of which is a tiny bar magnet for quantum mechanical reasons, line themselves up so their tiny magnets point in the same direction. These groups of atoms are called domains, and a piece of iron will be magnetic when all its domains line up too. That creates one macroscopic permanent magnetic field.
I say permanent because the magnetic field is not induced by an external source. That permanent field can be destroyed if the order of the magnetic domains is destroyed.
You may remember that when you heat up a substance you make its particles vibrate faster. Eventually they will vibrate fast enough to overcome the forces holding them together and change state (e.g. solid to liquid).
When you heat iron until it melts, you make its atoms vibrate so fast that their tiny little bar magnets no longer align, destroying the magnetic domains and hence the permanent field. You don’t even need to melt iron to do this. Heating a magnet to a sufficiently hot temperature will destroy the magnetic order.
The atoms in iron are basically all little magnets themselves, so a chunk of iron will be magnetic if all those little magnets are (mostly) lined up with each other. If they aren’t then they all point in different directions and cancel each other out.
So in a liquid all the atoms are moving around all the time, and they are being too jostled and shaken to line up, so liquid iron won’t be magnetic. In fact, [this happens before the iron even melts — even solids will have too much shaking from thermal energy to support magnetism if the temperature is high enough.](https://en.wikipedia.org/wiki/Curie_temperature)
You *can* kind of make a liquid magnet. First, if you *apply* a strong magnetic field to liquid metal you could (at least in principle) force all those little magnets to line up again. It’d take a super-strong field to do this in most cases, but theoretically it could be done if you had such a field. Of course, this would fall apart almost immediately after the external field went away.
Perhaps more practically, you can make a magnetic liquid-like thing by floating a bunch of little tiny solid magnets in a liquid. These are called “[ferrofluids](https://en.wikipedia.org/wiki/Ferrofluid)” and [they have super cool properties!](https://www.youtube.com/watch?v=5APHa7vscoI)
Ferro fluid exists this ELI5 isnt needed is it?
In order for large scale magnetic fields to form from a material, you have to align the magnetic fields of the atoms so that they add together instead of cancelling out when oriented randomly.
Liquid iron is paramagnetic, which means you can produce a magnetic field from it in the presence of an external magnetic field (it can nudge enough atoms into alignment to add to the external field), but once removed due to the fluidity and temperature (remember that at atomic scales, temperature = movement) that alignment collapses and randomness/cancelling out wins.
Magnetism can only be observed in a material with atoms that are (mostly) aligned in the same direction. Atoms in liquids are free to move around and as such even if we could make them align the effect would be lost almost instantaniously.
Basicaly, imagine metalic iron like a box full of aples that were tightly stacked so all of them have their stems facing up. Now to imagine liquid iron shake the box of apples really hard. The apples (atoms) are no longer stacked like they were before and the material they represent has lost its magnetic properties.
We do have liquid magnets, they’re called ferrofluids.
You can think of the structure of the solid metal as a slide and charge flows naturally in one direction. And if someone melts the slide it no longer can do that. This is an extremely oversimplified explanation. You can think of otherwise non magnetic solids something that doesn’t have passive quality for guiding the flow of water or electrons.
On a chemical/physical level the ions in the metal have to all be aligned so that charge flows in one direction which creates magnetism. If you get the metal you unalign everything, after cooling it would no longer be magnetic.
In order for a material to be magnetic it needs to be made out of molecules that are 1) polarized and 2) organized in such a way that all the north and south poles are aligned with eachother.
When you heat up iron, the molecules tend to align in random directions, so the magnetism is lost. Depending on how it cools down, it may lose magnetism even after it turns back to solid.
You may want to read about Curie points, its the temperature at which materials loose their magnetism. This is lower than materials melting point. You can make a permanent magnet non magnetic by heating the.
This can be used in practical applications, such as rice cookers! When the water is evaporated, heat goes above the boiling point and a material with a Curie point just above boiling becomes nok magnetic, making a permanent magnet no longer stick to it and a spring separates the two, and cuts the connection to the heating element.
Technology connections have an excellent video to it.
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