Cause of magnetism
1. Electrons, protons, neutrons all posses magnetic moment due to both orbital & spin motions. This magnetic moment is ultimately responsible for magnetism.
2. due to spin is also called intrinsic magnetic moment or permanent magnetic moment & can be understood using quantum mechanics only.
3. associated with the orbital motion of a charge can be explained even by classical concepts, for it an electron orbiting around a nucleus in a circle or radius r at a velocity v it is
4. The minimum value of produced due to the orbital motion of an electron around an atomic nucleus is called Bohr magneton (μ).
5. The nuclear magnetic moment typically is much smaller than the electron magnetic moment .
6. Net magnetic moment of an atom is the vector sum of is magnetic moments of all of its electrons, protons & neutrons, both due to orbital motion & as well as spin motion.
7. Generally magnetic moments of atoms are randomly aligned & thus for any volume containing more than several thousand atoms net dipole moment is usually zero (for all types of material, dia, para, ferro).