- Every substance possesses magnetic properties originated from the electrons present in them.
- Each electron in an atom behaves like a tiny magnet.
- The magnetic moment of these substances originates from two types of motions
- its orbital motion around the nucleus and
- its spin around its own axis.
- Electron being a charged particle undergoes these motions and can be considered as a small loop of current possessing a magnetic moment.
- Therefore, each electron has a permanent spin and an orbital magnetic moment associated with it.
- Magnitude of this magnetic moment is very small and is measured in the unit called Bohr magneton, μ B and is equal to 9.27 × 10–24A m2.
On the basis of their magnetic properties, substances can be classified into five categories: