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Most questions about this ask why, or how, a neutron has a magnetic moment at all, or why it is negative....

But I am curious as to what it means, physically or experimentally, for a magnetic moment to be 'negative'....

I am reading that a neutron's 'angular-momentum' spin is pointing in the opposite direction of its 'magnetic-moment' spin, but I thought that the quantum spin of a particle WAS its magnetic moment spin....

At any rate, what experiment(s) showed that neutrons have a 'negative' magnetic moment spin? Maybe reading about that will help...

Edit: P.S.: I still don't understand how a neutron's negative magnetic moment is actually manifested... Perhaps an antiproton or electron, being negatively charged, is antiparallel, or whatever, but a neutron is neutral....

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It means that a neutron’s magnetic moment vector is in the opposite direction from its spin angular momentum vector.

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  • $\begingroup$ But, what does that actually mean? Physically? What was the experimental or observational evidence? $\endgroup$
    – Kurt Hikes
    Jul 2 '21 at 23:24
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Suppose that a spinning body has equal amounts of positive and negative charge --- so its total charge is zero --- and the positive charge is near the rotation axis, while the negative charge is further away from the axis. Then the magnetic moment will point in the opposite direction to the spin. Presumably this is a classical model of the charge distribution in a neutron.

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  • $\begingroup$ Deep inelastic scattering suggests the neutron has a negatively-charged "core," a positively-charged "mantle," and a negatively-charged "halo"; see here. $\endgroup$
    – rob
    Jul 3 '21 at 1:50

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