MP Board · Class 12 · Physics · Magnetism and MatterDifferentiate between Diamagnetic, Paramagnetic, and Ferromagnetic substances on the basis of their magnetic properties. Give at least five points of distinction and provide two examples for each.

Introduction\nMagnetic substances are classified into three major categories based on their response to an external magnetic field: diamagnetic, paramagnetic, and ferromagnetic. This classification depends on their magnetic susceptibility, permeability, and behavior at varying temperatures.

Points of Distinction

1. Behavior in an External Magnetic Field:

   • Diamagnetic: Repelled weakly by a strong magnetic field. They move from stronger to weaker parts of a magnetic field.
   • Paramagnetic: Attracted weakly by a magnetic field. They move from weaker to stronger parts of a field.
   • Ferromagnetic: Strongly attracted by a magnetic field. They quickly move towards the stronger parts of a field.

2. Magnetic Susceptibility ($\chi$):

   • Diamagnetic: Small and negative ($-1 \le \chi < 0$).
   • Paramagnetic: Small and positive ($0 < \chi < \epsilon$).
   • Ferromagnetic: Very large and positive ($\chi \gg 1$).

3. Magnetic Permeability ($\mu$):

   • Diamagnetic: Slightly less than unity ($0 \le \mu < 1$).
   • Paramagnetic: Slightly greater than unity ($\mu > 1$).
   • Ferromagnetic: Very large ($\mu \gg 1$).

4. Effect of Temperature:

   • Diamagnetic: Their magnetic susceptibility is independent of temperature.
   • Paramagnetic: Their susceptibility is inversely proportional to absolute temperature (Curie's Law, $\chi \propto 1/T$).
   • Ferromagnetic: Their susceptibility decreases with temperature and above the Curie temperature ($T_c$), they become paramagnetic.

5. Atomic Structure/Domain Theory:

   • Diamagnetic: Atoms have paired electrons resulting in a net zero magnetic moment.
   • Paramagnetic: Atoms have unpaired electrons with individual magnetic moments that are randomly oriented.
   • Ferromagnetic: They possess microscopic regions called domains where magnetic moments are strongly aligned in one direction.

6. Examples:

   • Diamagnetic: Bismuth, Copper, Water, Gold.
   • Paramagnetic: Aluminium, Sodium, Calcium, Oxygen.
   • Ferromagnetic: Iron, Cobalt, Nickel, Alnico.