Electromagnetism

3Magnetic Media

3.1. Introduction: orbital and spin magnetic moments

It is currently posited that electrons in an atom rotate around the nucleus in the form of orbitals and around themselves as spins.

The magnetic field exists in a vacuum, obeying the laws of magnetism.

The magnetic moment (see Figures 3.1 and 3.2) can be associated with a current induced by the movement of an electron in its orbit. This classic description of the orbital magnetic moment of an electron can provide elements for an interpretation of certain magnetic properties of matter; however, in general, only a quantum theory can rigorously account for the magnetic properties of matter.

Therefore, the associated magnetic moment is given by:

Alfred Landé (1888–1976), a German quantum physicist, gave an explanation of the Zeeman effect: splitting of atom lines under a magnetic field.

For a color version of all figures in this book, see www.iste.co.uk/gontrand/electromagnetism.zip.

Figure 3.1. Magnetic moment

COMMENTS ON FIGURE 3.1.– Orbital magnetic moment of the electron according to Bohr’s model (Niels Henrik David Bohr 1885–1962, Copenhagen): the electron describes a circle around the atom, of radius r, ...