Earth's magnetic field -- How can there be a field when the Earth's core is above the Curie temperature?

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Luiz Felipe Ramos
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We know that when a magnet is exposed to high temperatures, it loses its magnetic properties. Why then does the Earth's magnetic field behave differently? That is, why doesn't the Earth lose its magnetic properties? According to BBC News Brasil, the core temperature is around 6000 ° C, higher than the Curie point for iron and nickel components.

Attachment:

https://www.bbc.com/portuguese/noticias/2013/04/130428_terra_temperatura_nucleo_sol_rw - Access date: 07/02/2021.

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  • #3
Vanadium 50
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How can there be a magnetic field from a copper coil when copper doesn't even have a Curie temperature?
 
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kuruman
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All magnetic fields are caused by electric currents, of one form or another.
I think magnetic fields from permanently magnetized materials should be excluded. Yes, one can use magnetization currents to model such fields but one has to be careful not to take this idea literally. My concern is that one might lose sight of the magnetic moment of the electron as one of its intrinsic properties.
 
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davenn
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I think magnetic fields from permanently magnetized materials should be excluded. Yes, one can use magnetization currents to model such fields but one has to be careful not to take this idea literally. My concern is that one might lose sight of the magnetic moment of the electron as one of its intrinsic properties.

You quoted @PeroK

But I don't understand if you are arguing against his link ( which is appropriate for the thread) or what your point is ?
 
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vanhees71
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I think magnetic fields from permanently magnetized materials should be excluded. Yes, one can use magnetization currents to model such fields but one has to be careful not to take this idea literally. My concern is that one might lose sight of the magnetic moment of the electron as one of its intrinsic properties.
That's underlined by the fact that the gyrofactor is around ##2## for the intrinsic magnetization of the electron due to its spin (which is a result of minimal coupling of the em. field and can be derived both within relativistic (Dirac equation) and non-relativistic (Pauli equation) when the "minimal coupling" is done right ;-)).

For a magnetization due to a current the gyro factor is 1.
 
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kuruman
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You quoted @PeroK
But I don't understand if you are arguing against his link ( which is appropriate for the thread) or what your point is ?
I was not arguing against the link. I was trying to clarify to OP that, in a permanent magnet below the Curie point, the existing magnetic field is not generated by currents of the charge transport variety. My objection was to the sweeping use of "all" as in "All magnetic fields are caused by electric currents".
 
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