The Electron Theory of Magnetism

The paramagnetic, diamagnetic and ferromagnetic behavior of substances can be explained in an elementary way in terms of the electron theory of matter.

Each electron is supposed to be revolving in an orbit around the nucleus. Each moving is supposed to be revolving in an orbit around the nucleus. Each moving electron behaves like a tiny current loop and therefore possesses orbital magnetic dipole moment. Furthermore, each electron is spinning about an axis through itself. This spin also gives rise to a magnetic dipole moment. In general, the resultant magnetic dipole moment of an atom is the vector sum of the orbital and spin magnetic dipole moments of its electrons.

Explanation of Diamagnetism

Diamagnetism occurs in those substances whose atoms consist of an even number of electrons. The electrons of such paired. The electrons in each pair have orbital motions as well as spin motions in opposite sense. The resultant magnetic dipole moment of the atom is thus zero. Hence when such a substance is placed in a magnetic field, the field does not ten to align the atoms (dipoles) of the substances.

Explanation of Para magnetism

In paramagnetic materials, the magnetic fields associated with the orbiting and spinning electrons do not cancel out. There is a net intrinsic moment in it. The molecule in it behaves like little magnets. When such a substance is placed in an external magnetic field, it will be turn and line up with its axis parallel to the external field.

Explanation of Ferromagnetism

Ferromagnetic substances are very strongly magnetic. The best-known examples of ferromagnets are the transition metals Fe, Co, and Ni. A ferromagnetic has a spontaneous magnetic moment – a magnetic moment even in zero applied fields. The atoms (or molecules) of ferromagnetic materials have a net intrinsic magnetic dipole moment which is primarily due to the spin of the electrons.