The response of a material to an applied field and its magnetic hysteresis is an essential tool of magnetometry. Paramagnetic and diamagnetic materials can easily be recognised, soft and hard ferromagnetic materials give different types of hysteresis curves and from these curves values such as saturation magnetisation, remanent magnetisation and coercivity are readily observed. More detailed curves can give indications of the type of magnetic interactions within the sample.
Hysteresis is a subject which covers a wide range of behaviour in materials, both in magnetism and other disciplines. The aim of this section is to cover the basic principles of the use of hysteresis as a probe of magnetism.