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What is the Magnetization of a Material?

Answer #1

Level 3 (with higher mathematics)
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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).

    Magnetization Weakens External Magnetic Field (Diamagnetism)
    The magnetization of the material weakens the external magnetic field \(B\) in the material (diamagnetism).
  • If the magnetic susceptibility is positive: \( \chi \gt 0 \), then the material is paramagnetic.

    Magnetization Amplifies External Magnetic Field (Paramagnetism)
    The magnetization of the material slightly amplifies the external magnetic field \(B\) in the material (paramagnetism).
  • If the magnetic susceptibility is much greater than zero: \( \chi \gg 0 \), then the material is ferromagnetic.