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What is magnetic susceptibility used to measure?

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Learn about magnetic fields and the levels of particles, atoms, crystals, and domains — magnet Magnetic fields and the levels of magnetism of particles, atoms, crystals, and domains.

Magnetic susceptibility is a quantitative measure of the extent to which a material becomes magnetized when placed within an applied magnetic field.1

Mathematically, it is defined as the ratio of the magnetization ( $M$ ) within a material to the applied magnetic field strength ( $H$ ), expressed as $χ_{m} = M / H$ . This value allows scientists to classify materials into three primary categories based on their magnetic response:12

Diamagnetic materials: Characterized by small, negative susceptibility values, these materials slightly expel an external magnetic field.12
Paramagnetic materials: These possess small, positive susceptibility values, indicating they slightly enhance an external magnetic field.1
Ferromagnetic materials: These exhibit large, positive susceptibility values, as they are composed of domains that align easily with an external field, resulting in significant magnetization.12

By measuring the force exerted on a substance within an inhomogeneous magnetic field, researchers can accurately determine a material's susceptibility, providing insight into its fundamental magnetic properties.2