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I don't know much about electromagnetism and magnetism, but I do understand some things. Recently, a question has been going around my head, so I did some research of my own, and now I'm confused and need help. I've read that magnetism is caused by the movement of charged particles, like if most of the electrons move in the same direction, the object reacts with a magnet, like iron or nickel. But, I want some more detailed information on magnetism. For example, does the direction of the spin of the electron affect the way of reaction with a magnet? Also, I've seen on the internet that paramagnetism(the weak attraction towards a magnet) is caused by the unpaired electrons in an atom. Due to their spin, unpaired electrons have a magnetic dipole moment and act like tiny magnets. But, Copper, having one unpaired electron, repels a magnet. Why does this happen?

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  • $\begingroup$ This video may help - MAGNETS: How Do They Work? $\endgroup$
    – mmesser314
    Aug 18, 2022 at 14:23
  • $\begingroup$ But I still didn't understand why Copper 'repels' a magnet? Isn't supposed to be paramagnetic and 'attract' weakly since it has one unpaired electron? $\endgroup$ Aug 18, 2022 at 14:39
  • $\begingroup$ Copper doesn't repel magnets. If you sit a piece of copper and a magnet beside each other nothing happens. But eddy currents induced in a non-magnetic conductor (not just copper) can turn it into a pseudo-electromagnet which can. I am guessing you are omitting or not noticing the context of when you presumably saw copper repel a magnet. $\endgroup$
    – DKNguyen
    Aug 18, 2022 at 14:48
  • $\begingroup$ Ok that says a lot but it'd be helpful if you could elaborate it a bit, I mean how exactly does it happen, like at an atomic level, and what is a pseudo-electromagnet(I've searched the internet about pseudo-electromagnets and all the definitions seem pretty confusing that's why I'm asking here I'll be really grateful if it's explained in a brief and simple manner). Btw thanks for your answer! $\endgroup$ Aug 18, 2022 at 14:55

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Magnetism can be caused by two things. The spin of particles or charged particles that move.

The spin of a particle not only acts as an intrinsic magnetic dipole (a tiny magnet) but it is also the source of rules on how can we stack particles (specifically fermions) and magnetic moments together. For example, if two electrons want to be in the same low energy state of helium, one has to be spin up and other spin down per Pauli's exclusion principle (providing zero net electronic magnetic moment).

Electrons that orbit an atom are also a source of magnetism as their orbit has an associated angular momentum and thus a magnetic moment. For charged particles moving there are actually two effects, there is the Zeeman interaction (the usual alignment of the magnetic moment along the field) and the Larmor diamagnetism (the fact that if they move their orbits gets modified by the magnetic field and the particles want to cancel the effect of the magnetic field, it is analogous to precession as in Larmor precession).

In the case of copper it is the diagmagnetic contributions that wins and its total magnetic moment tends to (weakly) align copper samples against the magnetic field. So the usual "paramagnetism (the weak attraction towards a magnet) is caused by the unpaired electrons in an atom" does not apply because it misses Larmor diamagnetism. Note that the same happens for gold.

Note that I could try to give you a classical picture on how this works, but eventually all fails as magnetism in matter is inherently a quantum phenomenon per the Bohr-Van Leeuwen theorem

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I want some more detailed information on magnetism.
Our idea of the electron as an electric elementary charge often overshadows the fact that the electron is to the same extent an intrinsic magnetic dipole. Yet no one asks what makes the electron an electric charge. Likewise, it must be assumed that the electron has a magnetic dipole under all circumstances - i.e. intrinsically.

For example, does the direction of the spin of the electron affect the way of reaction with a magnet?
In the past it was assumed that an electron must rotate in order to generate a magnetic field. A short time later, this turned out to be untenable. Nevertheless, the concept of spin has remained.

In a permanent magnet, the magnetic dipoles (spins) of subatomic particles - mostly the electrons, but also the protons - are aligned in sum so that a macroscopic magnetic field exists. So when interacting with a metal, just remember that the magnet now influences the subatomic particles of the metal and their magnetic dipoles (spins) align along the macroscopic field.
As you can see from the brackets, the word spin is unnecessary and explains no more than if you leave it out straight away.

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