from the Dirac equation one can straightforwardly derive that in the nonrelativistic limit, the Hamiltonian of a charged particle in a magnetic field acquires a term(adsbygoogle = window.adsbygoogle || []).push({});

[tex]-\vec{\mu} \cdot \vec{B}[/tex]

which shows the particle has an intrinsic magnetic moment (by analogy with the classical expression of the energy of a magnetic dipole in a magnetic field). Contrary to the classical case however, this moment is not sustained by a current (at least that is not the mainstream thought).

Now, looking at this classically the energy of an electron in a magnetic field causes a force if the field is inhomogeneous

[tex]\vec{F}=-\nabla(-\vec{\mu} \cdot \vec{B})=\nabla(\vec{\mu} \cdot \vec{B})[/tex]

So the electron starts moving right? Now what force is responsible for this movement, who does the work?

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# Spin in magnetic field: work?

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