BH curves (hysteresis loops) in magnets are important for characterizing their magnetic properties. They complement the physical data of magnets. They illustrate the relationship between magnetic induction (B) and magnetic field strength (H) in a given material. The main uses of BH curves include:

1. Determination of magnetic hardness and softness
   • Hard magnetic materials (permanent magnets) have a wide hysteresis loop with high remanence and coercivity.
   • Soft magnetic materials (e.g., transformer sheets) have a narrow hysteresis loop, meaning low losses when the magnetic field changes.
2. Determination of remanence (Br)
   • Remanence indicates the magnetic induction that a material retains after the external magnetic field is removed.
3. Determination of coercivity (Hc)
   • Coercivity determines how strong an opposing field is needed to nullify magnetization. The higher the value, the more resistant the magnet is to demagnetization.
4. Maximum magnetic energy (BHmax)
   • This point on the curve determines how much maximum energy the magnet stores and how effectively it can operate in its application.
5. Hysteresis losses
   • The width of the loop indicates energy losses during cyclic changes in the magnetic field, which is crucial for materials used in electric motors and transformers.

BH curves are important in the development of magnetic materials according to desired properties in various applications, from electric motors to sensors and magnetic storage.

See also physical properties of magnets and magnet surface treatments.