A Brief Theory of Magnetization

In diamagnetic and paramagnetic materials, small applied magnetic fields lead to an internal magnetic induction that is directly proportional to the applied field through 

We should note that many authors call B, not H, the magnetic field as induction already has other meanings in electrodynamics (such as induction of an electric field 

For ferromagnetic materials, the internal field H t cannot be approximated by the external H field and the B field can be expressed as 

Magnetization M, is defined as the magnetic moment per unit volume, and magnetic susceptibility %, is the ratio of magnetization divided by the macroscopic H field  

Similarly, the permeability of the medium is given by the ratio of the B and H fields  

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