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The Weiss magneton was experimentally derived in 1911 as a unit of magnetic moment equal to 1.53 × 10 −24 joules per tesla, which is about 20% of the Bohr magneton. In the summer of 1913, the values for the natural units of atomic angular momentum and magnetic moment were obtained by the Danish physicist Niels Bohr as a consequence of his ...
The electron is a charged particle with charge − e, where e is the unit of elementary charge. Its angular momentum comes from two types of rotation: spin and orbital motion. From classical electrodynamics, a rotating distribution of electric charge produces a magnetic dipole, so that it behaves like a tiny bar magnet.
This is the basis for defining the magnetic moment units of Bohr magneton (assuming charge-to-mass ratio of the electron) and nuclear magneton (assuming charge-to-mass ratio of the proton). See electron magnetic moment and Bohr magneton for more details.
where N is the Avogadro constant, g is the Landé g-factor, and μ B is the Bohr magneton. In this treatment it has been assumed that the electronic ground state is not degenerate, that the magnetic susceptibility is due only to electron spin and that only the ground state is thermally populated.
Atomic units are chosen to reflect the properties of electrons in atoms, which is particularly clear in the classical Bohr model of the hydrogen atom for the bound electron in its ground state: Mass = 1 a.u. of mass; Charge = −1 a.u. of charge; Orbital radius = 1 a.u. of length; Orbital velocity = 1 a.u. of velocity [44]: 597
The above classical relation does not hold, giving the wrong result by the absolute value of the electron's g-factor, which is denoted g e: = | | =, where μ B is the Bohr magneton. The gyromagnetic ratio due to electron spin is twice that due to the orbiting of an electron.
The spin magnetic moment of the electron is =, where is the spin (or intrinsic angular-momentum) vector, is the Bohr magneton, and = is the electron-spin g-factor. Here μ {\displaystyle {\boldsymbol {\mu }}} is a negative constant multiplied by the spin , so the spin magnetic moment is antiparallel to the spin.
It is approximately equal to one Bohr magneton, [85] [d] which is a physical constant that is equal to 9.274 010 0657 (29) × 10 −24 J⋅T −1. [86] The orientation of the spin with respect to the momentum of the electron defines the property of elementary particles known as helicity .