Magnetic Moment of an Electron

An electron revolving around a nucleus acts like a current loop. The orbital motion generates a current, and the product of this current and the orbital area produces the orbital magnetic dipole moment. This moment relates directly to the electron's orbital angular momentum, though it points antiparallel due to the electron's negative charge.

The Bohr magneton is the fundamental unit of magnetic dipole moment, with a value of 9.27 × 10⁻²⁴ Am². Since orbital angular momentum is quantized in multiples of the reduced Planck's constant, the electron's magnetic dipole moment is quantized in terms of Bohr magnetons, similar to charge quantization.

Electrons possess both orbital and spin angular momentum, each producing associated magnetic moments. The orbital moment and spin magnetic moment, approximately one Bohr magneton, combine vectorially to give the net magnetic moment. This vector sum determines the overall magnetic properties in materials.

The electron carries a negative charge, which reverses the direction of the magnetic moment relative to its orbital angular momentum. While the orbital angular momentum points in one direction based on the electron's motion, the resulting magnetic dipole moment points in the opposite direction due to this charge inversion.

Saturation magnetization equals the number of atoms per unit volume multiplied by the magnetic moment per atom. The number of atoms per unit volume is calculated using density, Avogadro's number, and atomic mass. For iron with density 7.87 g/cm³ and net moment 2.2 Bohr magnetons per atom, saturation magnetization is approximately 1.73 Am².

Since orbital angular momentum is quantized in multiples of the reduced Planck's constant, the magnetic dipole moment derived from it is also quantized. Each allowed angular momentum state corresponds to a discrete magnetic moment value expressed in units of the Bohr magneton, creating discrete energy levels in magnetic fields.

The electron's negative charge causes its magnetic moment to point opposite to its orbital angular momentum vector. This antiparallel relationship is a direct consequence of the charge sign; a positive charge would produce a parallel alignment. This directional reversal is fundamental to understanding electron magnetism.