# What is the Magnetization of a Material?

Level 3 (up to Physics B.Sc.)

The magnetization $$\boldsymbol{M}$$ describes the magnetic properties of a material. It is formed by the sum of all atomic magnetic moments $$\boldsymbol{\mu}$$ per volume $$V$$:

Definition of magnetization
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If you apply an external magnetic field $$\boldsymbol{H}$$ (or equivalently $$\boldsymbol{B}$$) and place a material into this magnetic field, the material will behave differently depending on the magnitude of the magnetization:

Magnetization depends on the external magnetic field
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Here $$\chi$$ is the magnetic susceptibility, which determines how good a material can be magnetized.

• If the magnetic susceptibility is negative: $$-1 \lt \chi \lt 0$$, then the material is diamagnetic. (Note that $$\chi$$ cannot be less than -1. A superconductor has $$\chi = -1$$ and is a perfect diamagnet).

• If the magnetic susceptibility is positive: $$\chi \gt 0$$, then the material is paramagnetic.

• If the magnetic susceptibility is much greater than zero: $$\chi \gg 0$$, then the material is ferromagnetic.