In November 1845, Michael Faraday discovered that heavy glass, bismuth, water, and organic tissue are weakly repelled by strong magnetic field gradients.
Classification of Magnetic Susceptibility ($\chi_m$)¶
Faraday categorized all matter into two primary magnetic classes:
- Diamagnetic Materials ($\chi_m < 0$): Induced magnetic dipoles oppose external magnetic field $\mathbf{B}$, causing weak repulsion (e.g., bismuth, water, copper).
- Paramagnetic Materials ($\chi_m > 0$): Induced magnetic dipoles align with external magnetic field $\mathbf{B}$, causing weak attraction (e.g., aluminum, platinum, oxygen).
$$\mathbf{M} = \chi_m \mathbf{H}$$
Quantum Magnetic Origin¶
Diamagnetism is a universal quantum property arising from orbital electron Larmor precession (Larmor diamagnetism).