2.1.4 Zeeman energy

For the energy of a magnetic body in an external field $\mathbf{H}_\mathrm{ext}$ we obtain

$$E_\mathrm{ext} = -\mu_0 \int_V \mathbf{M} \cdot \mathbf{H}_\mathrm{ext} \,d{^3r}\, \quad.$$

Due to the linearity of Maxwell's equations, the superposition principle allows a simple adding also of this energy term.